Meteorological disaster disturbances on the main crops in the north‒south transitional zone of China

Global climate change, with warming as its main feature, has altered the spatial-temporal evolution of factors such as precipitation and temperature that can cause meteorological disasters. The complex and changeable climate has led to frequent natural disasters, while the frequency and intensity of extreme climate events have also significantly increased, posing an enormous threat to societal production and human life. As the most important geoecological transitional zone of mainland China, the stability of agricultural production in China's north-south transitional zone is crucial for ensuring food security under climate change. With the use of daily precipitation and potential evapotranspiration data from 1961 to 2018, this study focused on analysing disturbances such as extreme precipitation and drought disasters at different time scales during the winter wheat and summer maize growing seasons in the north-south transitional zone of China from an agricultural production perspective and attempted to answer the following questions: first, from an agricultural production perspective, what are the temporal and spatial distribution patterns of extreme precipitation and arid climate events in the north-south transitional zone? Second, which areas are at high risk of being disturbed by different types of meteorological disasters and require increased attention? The results indicated that (1) in terms of the overall temporal variation, the degree of extreme precipitation and drought stress faced by agricultural production in the region is decreasing. However, the temporal variation at each station in the north-south transitional zone was not completely consistent with the overall trend, and both increasing and decreasing trends were observed. The sites exhibiting an increase overlapped with typical regions of the north-south transitional zone to varying degrees, indicating that the typical regions represented not only theoretical potential risk areas under climate change but also suffered from meteorological disaster disturbances. (2) The precipitation distribution during the winter wheat growth period in the south-north transitional zone was uneven and varied significantly. High values of extreme precipitation indices during the winter wheat growth period were mainly concentrated in the southern part of the eastern section of the north‒south transitional zone. The precipitation distribution during the summer maize growth period significantly differed, with the highest amount of heavy rain and largest number of rainstorm days concentrated in the southeastern part of the north‒south transitional zone. The spatial distribution of the drought frequency in the north-south transitional zone, as indicated by the monthly standardized precipitation evapotranspiration index (SPEI1), showed that the areas with high total drought frequencies were mainly concentrated in northeast Jiangsu, southeast Henan, and north Anhui, which primarily experienced light drought. The central part of Jiangsu Province exhibited a high frequency of moderate drought, while southern Jiangsu Province and southwestern Shaanxi Province were prone to severe drought. Additionally, southeastern Hebei and eastern Henan were identified as areas with a high frequency of extreme drought. Finally, the central region of Sichuan Province was characterized by both severe and extreme drought conditions. Based on the SPEI12-derived spatial distribution of the drought frequency in the north-south transitional zone, the areas with a high total drought frequency were mainly concentrated in central and eastern Henan, southeast Shaanxi, southeast Shandong, and central Sichuan, which primarily experienced light to moderate drought. The northwestern part of Jiangsu, the southern part of Hebei, and the western part of Shandong are regions with a high frequency of severe drought, while the eastern part of Henan is an area with high frequencies of both severe and extreme drought. (3) High-value areas of extreme precipitation and drought disturbance in the north-south transitional zone overlapped with the edge of the transitional zone to varying degrees. Approximately 63.58% of the north‒south transitional zone of China was characterized by moderate or high stress levels, primarily concentrated along the southern boundary and central core area, and nearly 39.5% of all counties experienced two or more types of disaster stresses.

Assessing the feasibility and sustainability of a surfactin production process: a techno-economic and environmental analysis

Biosurfactants have been profiled as a sustainable replacement for chemical-based surfactants since these bio-based molecules have higher biodegradability. Few research papers have focused on assessing biosurfactant production to elucidate potential bottlenecks. This research aims to assess the techno-economic and environmental performance of surfactin production in a potential scale of 65m3, considering different product yields and involving the European energy crisis of 2021-2022. The conceptual design, simulation, techno-economic, and environmental assessments were done by applying process engineering concepts and software tools such as Aspen Plus v.9.0 and SimaPro v.8.3.3. The results demonstrated the high economic potential of surfactin production since the higher values in the market offset the low fermentation yields, low recovery efficiency, and high capital investment. The sensitivity analysis of the economic assessment elucidated a minimum surfactin selling price between 29 and 31 USD/kg of surfactin, while a minimum processing scale for economic feasibility between 4 and 5 kg/h is needed to reach an equilibrium point. The environmental performance must be improved since the carbon footprint was 43 kg CO2eq/kg of surfactin. The downstream processing and energy demand are the main bottlenecks since these aspects contribute to 63 and 25% of the total emissions. The fermentation process and downstream process are key factors for future optimization and research.

Water stress significantly affects the diurnal variation of solar-induced chlorophyll fluorescence (SIF): A case study for winter wheat

Remote sensing of Solar-induced chlorophyll fluorescence (SIF) has been widely used in estimating Gross Primary Productivity (GPP) and detecting stress in terrestrial ecosystems. Water stress adversely impacts the growth, development, and productivity of a plant. Recently, the characterizing and understanding of the diurnal cycling of plant functioning and ecosystem processes has been explored using SIF. However, the diurnal response of SIF to different levels of water stress remains unclear. This study conducted field experiments on winter wheat by subjecting it to different levels of water stress including well-watered (CK) and, mild, moderate, and severe water stress (D1, D2, D3), and collected the spectral data using an automated SIF measurement system. The results observed the strong SIF-PAR (photosynthetically active radiation) correlations and that these relationships gradually decoupled with increasing water stress, which further decreased the accuracy of temporal upscaling of far-red SIF from an instantaneous to daily scale. To quantify the characteristics of diurnal far-red SIF, five indices including peak time, peak value, curve opening coefficient (leading coefficient of the parabola), and left/right slopes of the peak were proposed. The results demonstrated that diurnal far-red SIF was characterized by an earlier peak time, decreasing peak value, wider curve opening, and flattening right slope from the CK plot to the D3 plot. There were certain mechanisms linking the different indices, for example, between peak size and opening coefficient. Furthermore, the response of far-red SIF to water stress was most pronounced at noon. SIF/PAR exhibited a more significant response to varying water stress compared to far-red SIF, which mitigated the negative influence of PAR variations on diurnal SIF. These findings contribute to the monitoring of plant water dynamics at fine temporal scales.

Future climate change impacts on wheat grain yield and protein in the North China Region

The threat of global climate change on wheat production may be underestimated by the limited capacity of many crop models to predict grain quality and protein composition. This study aimed to integrate a wheat quality module of protein components into the CROPSIM-CERES-Wheat model to investigate the impact of climate change on wheat grain yield and protein quality in the North China Region (NCR) using five Global Climate Models (GCMs) from CMIP6 under three shared socioeconomic pathways. The CERES-Wheat model with a quality module was developed and calibrated and validated using data from several sites in the NCR. The results of the calibration and validation showed that the modified CERES-Wheat model can accurately predict grain yield, protein content and its components in field experiments. Compared with the baseline period (1981-2010), the annual mean temperature and annual cumulative precipitation increased in the NCR in the 2030's, 2050's and 2080's. The radiation was higher under the SSP126 and SSP585 scenarios, and lower under the SSP370 scenario compared to the baseline period. The anthesis and maturity date occurred earlier under the three future scenarios. The average grain yield increased by 13.3-30.9 % under three future scenarios. However, the regional average grain protein content of winter wheat in the future decreased by 2.0 %- 3.5 %. The reduction in wheat grain protein at the regional was less pronounced under SSP370 than that under SSP126 and SSP585. The structural protein content of winter wheat decreased under future climate conditions compared with the baseline period, but the storage protein content showed the opposite tendency. The model provided a useful tool to study the effects of future climate on grain quality and protein composition. These findings are important for developing agricultural practices and strategies to mitigate the potential impacts of climate change on wheat production and wheat quality in the future.

Metabolomics reveals the impact of nitrogen combined with the zinc supply on zinc availability in calcareous soil via root exudates of winter wheat (Triticum aestivum)

A possible mechanism for the improved availability of zinc (Zn) in soil by combining nitrogen (N) with Zn supply was investigated based on the root exudates of winter wheat. N, Zn supply as well as their combination significantly regulated nine root exudates in winter wheat; in which, the secretion of cis-aconitic acid involving in the TCA cycle, C5-branched dibasic acid metabolism, glyoxylate and dicarboxylate metabolism and 2-oxocarboxylic acid metabolism was upregulated by N, Zn supply as well as their combination. N-Zn combination induced the activities of citrate synthase and cis-aconitase in roots and shoots of winter wheat thus to increase the concentrations of citric and aconitic acid; the decrease of isocitric acid concentrations in shoots indicated the inhibited conversion of aconitic acid to isocitric acid by N-Zn combination. It revealed a possible reason for the enhanced secretion of cis-aconitic acid by N-Zn combination. Exogenous addition of 10 μ plant-1 cis-aconitate significantly increased available Zn concentrations in soil and Zn concentrations in winter wheat under N-Zn combination. Thus, the N-Zn combination regulated the metabolism of cis-aconitic acid in winter wheat, thus enhancing the secretion of cis-aconitic acid to increase the bioavailability of Zn in soil.

Nitrogen fertilization and precipitation affected Wheat (Triticum aestivum L.) in dryland the Loess Plateau of South Shanxi, China

Wheat (Triticum aestivum L.) is a staple crop worldwide, and its yield has improved since the green revolution, which was attributed to chemical nitrogen (N) fertilizer application. An experiment was conducted to set seven nitrogen application levels of N0, N90, N120, N150, N180, N210 and N240 kg ha^-1 before sowing. The results showed that grain yield under the nitrogen rate of N210 kg ha^-1 was significantly increase the water intake during jointing to anthesis, Soil water storage of dryland wheat in fallow period was higher than water consumption in jointing stage and the leaf area index at anthesis, the tiller percentage rate, the jointing-anthesis, and nitrogen accumulation were closely related to yield and its components. Nitrogen fertiliser rate N150 kg ha^-1 significantly increased dry matter buildup from jointing to flowering in dryland wheat compared to N fertiliser rate N210 kg ha^-1. The rise of nitrogen application rate, there were no significant variance in nitrogen accumulation of Stem + leaf sheath and cob + glume at maturity, respectively. N fertiliser rate N210 kg ha^-1 compared to N180 kg ha^-1 significantly reduced grain gliadin content in dryland wheat, respectively. Wheat crops under N210 kg ha^-1 could achieve both high NUE and grain yield simultaneously with only moderate N fertilizer in South Shanxi, China.

Estimating daily minimum grass temperature to quantify frost damage to winter wheat during stem elongation in the central area of Huang-Huai plain in China

Frost damage to winter wheat during stem elongation frequently occurred in the Huang-Huai plain of China, leading to considerable yield losses. Minimum Stevenson screen temperature (ST_min) and minimum grass temperature (GT_min) have long been used to quantify frost damage. Although GT_min has higher accuracy than ST_min, it is limited in application due to the lack of data. Therefore, this study aimed to select appropriate environmental variables to estimate GT_min, as well as to quantify the frost damage. Shangqiu, a frost-prone winter wheat area in the central Huang-Hui plain, was selected as the study area. From the descriptive statistics of ST, air relative humidity (RH), wind speed (WS), cloud fraction (CF), and volumetric soil water content (VWC) during temperature decreasing and increasing, seven variables significantly correlated with GT_min were selected, including ST_min, maximum reduction of ST (RST), maximum increase of ST (IST), minimum RH during temperature increasing (RH_min), WS at ST_min occurrence (WS), minimum VWC during temperature decreasing (VWC_min), and nightly CF. Multiple linear regression (MLR), support vector regression (SVR), random forest (RF), and K-nearest neighbor (KNN) were adopted for estimating GT_min based on the various combinations of the variables. Results showed the more variables, the higher the accuracy for the MLR and SVR. However, this pattern was not always true for the KNN and RF. The KNN based on ST_min, RST, IST, RH_min, and WS achieved the highest accuracy, with R² of 0.9992, RMSE of 0.14 ℃, and MAE of 0.076 ℃. The overall classification accuracy for frost damage identified by the estimated GT_min reached 97.1% during stem elongation of winter wheat from 2017 to 2021. The integrated frost stress (IFS) index calculated by the estimated and measured GT_min maintained high linear fitting accuracy. The KNN with fewer variables demonstrated good applicability at the regional scale.

Identifying genomic regions determining shoot and root traits related to nitrogen uptake efficiency in a multiparent advanced generation intercross (MAGIC) winter wheat population in a high-throughput phenotyping facility

In the context of a continuously increasing human population that needs to be fed, with environmental protection in mind, nitrogen use efficiency (NUE) improvement is becoming very important. To understand the natural variation of traits linked to nitrogen uptake efficiency (UPE), one component of NUE, the multiparent advanced generation intercross (MAGIC) winter wheat population WM-800 was phenotyped under two contrasting nitrogen (N) levels in a high-throughput phenotyping facility for six weeks. Three biomass-related, three root-related, and two reflectance-related traits were measured weekly under each treatment. Subsequently, the population was genetically analysed using a total of 13,060 polymorphic haplotypes and singular SNPs for a genome-wide association study (GWAS). In total, we detected 543 quantitative trait loci (QTL) across all time points and traits, which were pooled into 42 stable QTL (sQTL; present in at least three of the six weeks). Besides Rht-B1 and Rht-D1, candidate genes playing a role in gibberellic acid-regulated growth and nitrate transporter genes from the NPF gene family, like NRT 1.1, were linked to sQTL. Two novel sQTL on chromosomes 5 A and 6D showed pleiotropic effects on several traits. The high number of N-specific sQTL indicates that selection for UPE is useful specifically under N-limited conditions.

Selenium uptake, translocation, subcellular distribution and speciation in winter wheat in response to phosphorus application combined with three types of selenium fertilizer

BACKGROUND

Selenium (Se) deficiency causes a series of health disorders in humans, and Se concentrations in the edible parts of crops can be improved by altering exogenous Se species. However, the uptake, transport, subcellular distribution and metabolism of selenite, selenate and SeMet (selenomethionine) under the influence of phosphorus (P) has not been well characterized.

RESULTS

The results showed that increasing the P application rate enhanced photosynthesis and then increased the dry matter weight of shoots with selenite and SeMet treatment, and an appropriate amount of P combined with selenite treatment increased the dry matter weight of roots by enhancing root growth. With selenite treatment, increasing the P application rate significantly decreased the concentration and accumulation of Se in roots and shoots. P₁ decreased the Se migration coefficient, which could be attributed to the inhibited distribution of Se in the root cell wall, but increased distribution of Se in the root soluble fraction, as well as the promoted proportion of SeMet and MeSeCys (Se-methyl-selenocysteine) in roots. With selenate treatment, P_0.1 and P₁ significantly increased the Se concentration and distribution in shoots and the Se migration coefficient, which could be attributed to the enhanced proportion of Se (IV) in roots but decreased proportion of SeMet in roots. With SeMet treatment, increasing the P application rate significantly decreased the Se concentration in shoots and roots but increased the proportion of SeCys₂ (selenocystine) in roots.

CONCLUSION

Compared with selenate or SeMet treatment, treatment with an appropriate amount of P combined with selenite could promote plant growth, reduce Se uptake, alter Se subcellular distribution and speciation, and affect Se bioavailability in wheat.

Integrated microbiological and metabolomics analyses to understand the mechanism that allows modified biochar to affect the alkalinity of saline soil and winter wheat growth

In order to understand the mechanism that allows modified biochar (BC) to enhance the salt tolerance and growth of crops in saline-alkali soil, we tested the effects of ordinary BC, nanoparticle-size BC, acidified BC (HBC), and acidified nanoparticle-size BC on winter wheat growth and the soil properties by combining microbiological and metabolomics analyses. The results showed that compared with the control with no BC, the plant height increased by 17.33 % under HBC and the proportion of large soil aggregates increased by 1.25-2.83 times. HBC increased the relative abundances of some dominant genera of bacteria (e.g., Streptococcus) and fungi (e.g., Mycothermus), as well as functions such as bacterial metabolic genetic information processing and cellular processes, and reduced the abundance of pathotrophic fungi. Metabolomics analysis showed that HBC upregulated various metabolites (including amino acids and their derivatives, lipids, flavonoids, and organic acids) and five main metabolic pathways. Among the KEGG pathways, the pyrimidine metabolism pathway was significantly upregulated, as well as crop leaf metabolism, β-alanine metabolism, and valine, leucine, and isoleucine metabolism, and the antioxidant levels and resistance to salt-alkali stress were enhanced in winter wheat leaves. Partial least squares-path modeling suggested that HBC affected the growth of winter wheat by significantly changing the soil physicochemical properties and microbial structure (path coefficients of 0.566 and 0.512, respectively).

Multi-objective winter wheat irrigation strategies optimization based on coupling AquaCrop-OSPy and NSGA-III: A case study in Yangling, China

The contradiction between crop water requirements and water supplies in Guanzhong Plain of Northwest China restricts the production of local winter wheat. The optimization of irrigation strategies considering multiple-objectives is of great significance to alleviate water crisis and sustainability of winter wheat production. This paper considered three typical hydrological years (dry year, normal year, and wet year), and a simulation optimization model coupling AquaCrop and NSGA-III was developed using Python language. The multi-objective optimization problem considered four objectives: (1) maximize crop yield (Y), (2) minimize irrigation water (IW), (3) maximize irrigation water productivity (IWP), and (4) maximize water use efficiency (WUE). The TOPSIS-Entropy method was then adopted for decision-making based on the Pareto fronts which were generated by multi-objective optimization, thus facilitating the optimization of the irrigation strategies. The results show that AquaCrop model could accurately simulate the growth process of winter wheat in the study area, the relative error is acceptable. The R² of canopy cover (CC) is 0.75 and 0.61, and above ground biomass production (B) is 0.94 and 0.93, respectively. In the Pareto fronts, the difference between the maximum and minimum yield of winter wheat is 9.48 %, reflecting the diversity of multi-objective optimization results. According to the analysis results of this paper, the performance of different irrigation scenarios in each typical year varies greatly. The performance of the optimization in dry years is significantly better than that in normal years and wet years. The optimization of irrigation strategies and comparison of different scenarios play a positive role in improving the local water use efficiency, the winter wheat yield, as well as the sustainable development level of water resources.

Effects of climatic and cultivar changes on winter wheat phenology in central Lithuania

It is essential to understand how climate change and varieties affect crop phenology and yields to adapt to future climate change. The aim of this study was to analyse the phenological development trends of three winter wheat cultivars (1990-2020) to identify the most critical meteorological-climatic factors influencing the development and yield of the cultivars and to investigate the heat requirements for each phenological phase to reveal the potential of the different cultivars to adapt to the warming climate. The observed dates of green-up, the beginning of stem elongation, and the grain development advanced significantly, but the timing of maturity changed insignificantly during the period of 1990-2020. The most marked change was related to the shortening of the period from sowing to green-up. The green-up dates were related to the mean temperature of the period after sowing. The occurrence of stem elongation and grain development dates were negatively correlated with the mean temperature in May. Significant correlations were found between temperature and duration from sowing to green-up and positive from stem elongation to grain development. The change of cultivar led to earlier green-up and grain development dates, but cultivar choise had no influence on sowing, stem elongation, and maturity dates from 1990 to 2020. The newer cultivar Skagen was more successful in exploiting increased thermal resources. The heat requirements remained almost unchanged during the vegetative development period, while the heat amount required during the reproductive period increased by about 15%. These findings demonstrate that the choice of crop cultivars with higher thermal requirements may be an appropriate adaptation mean to achieve higher yields in response to climate change, at least in the middle latitudes.

Spatial and interdecadal differences in climatic suitability for winter wheat in China from 1985 to 2014

The evident climate jump after 2000 in China may have greatly influenced the production of winter wheat, which is one of the nation's major grain crops. To evaluate the impacts of climate change on winter wheat production and identify the climatic factors primarily responsible, we used daily meteorological data from 2244 stations and integrated indicators to examine the decadal changes in the potential plantable zone (PPZ), growth periods, and climatic suitability for winter wheat in China from 1985 to 1999 and from 2000 to 2014. The results showed the following: (1) The PPZ has decreased by approximately 9%, and the main reason may be the increased frequency of extreme cold events in northern China from 2000 to 2014. (2) In most of the PPZ, the suitable sowing date has been delayed, the potential maturity date has advanced, and total days during the potential growing season have significantly decreased because of the increasing temperature. (3) The suitable area and optimal area of winter wheat have significantly decreased by 9% and 13%, respectively. The changes in climatic suitability are affected by both temperature and radiation in the north, whereas the impact is more from precipitation in the south. The climate may be changing in a direction unsuitable for winter wheat. As global warming and climate extremes intensify in the future, winter wheat production may become more challenging, and adequate measures should be adopted to guarantee reliable and high yields.

Estimation of the net primary productivity of winter wheat based on the near-infrared radiance of vegetation

Quantifying net primary productivity (NPP) is important for understanding the global carbon cycle and for assessing ecosystem carbon dynamics. However, uncertainties remain in NPP estimation. Using winter wheat data obtained from an experimental station in 2019, this study evaluated the ability of the near-infrared radiance of vegetation (NIR_V,Rad) to estimate NPP at different time scales and established an estimation model based on NIR_V,Rad, where NIR_V,Rad was defined as the product of the normalized difference vegetation index (NDVI) and the near-infrared radiance. The results showed that the linear relationship between NIR_V,Rad and NPP was superior to the relationship between NPP and NDVI, enhanced vegetation index-2 (EVI2), and near-infrared reflectance of vegetation (NIR_V,Ref) at each time scale (hourly, daily, and growth period). The advantage of NIR_V,Rad was more evident on the hourly scale, in which the R² of NIR_V,Rad and NPP reached 0.77, whereas the R² values of the correlation of NDVI, EVI2, and NIR_V,Ref with NPP were 0.30, 0.16, and 0.14, respectively. There existed a strong linear relationship between absorbed photosynthetically active radiation, net photosynthetic rate, leaf area index, and NIR_V,Rad, which explained the good relationship between NIR_V,Rad and NPP. Through a comparative analysis of the various models, the NIR_V,Rad model was found to have the strongest ability to estimate NPP and the R², with the measured NPP reaching 0.81. The accuracy of NIR_V,Rad provides a new method for estimating NPP and a scientific basis for estimating NPP using high-resolution satellite remote sensing data on a regional scale.

Characteristics and influencing factors of carbon fluxes in winter wheat fields under elevated CO2 concentration

Elevated carbon dioxide (ECO₂) concentration has profound impacts on ecosystem carbon fluxes, with consequent changes in carbon sequestration and its feedback to climate change. Agroecosystem plays an essential role in global carbon sequestration. However, it is not well understood how the carbon fluxes of agroecosystem respond to increasing atmospheric CO₂ concentrations. In this study, an in-situ 2-year field experiment was conducted using open-top chamber with treatments including ambient CO₂ concentration (CK) and ambient plus 200 μmol mol^-1 (T) to investigate the characteristics and main factors influencing carbon fluxes during the 2017-2019 winter wheat growing seasons. Results showed that the dynamics of CO₂ fluxes under different treatments had similar seasonal trends, with the peak flux observed at the heading-filling stage. Compared to the CK, T treatment increased the cumulative amount of CO₂ (CAC) by 17.2% and 24.0% in 2017-2018 and 2018-2019 growing seasons, respectively. In addition, the seasonal CAC was highly dependent on treatment and varied with year, while there was no interactive effect of treatment and year (p > 0.05). ECO₂ concentration increased the biomass of wheat by an average of 8.28% over two growing seasons. There was a significant positive correlation between biomass and CAC, with biomass elucidating 52% and 76% of the variations in CAC under CK and T treatments, respectively. A good correlation was found between net ecosystem exchange (NEE) and environmental variables under different treatments. During the pre-milk ripening period, the NEE mainly depended on photosynthetically active radiation (PAR) and air temperature (Ta), while NEE was mainly controlled by PAR and soil water content (SWC) during the post-milk ripening period. Overall, the findings presented here demonstrate that the carbon exchange in wheat fields under different treatments serves as carbon sequestration, while ECO₂ concentration enhances the capacity of winter wheat fields to act as carbon sinks, which may have feedback to the climate system in the future.

Selenium uptake and accumulation in winter wheat as affected by level of phosphate application and arbuscular mycorrhizal fungi

Selenium (Se) is an advantageous element to crops. However, the influence of arbuscular mycorrhizal fungi (AMF), phosphate (P) and selenite in soil on Se uptake by winter wheat remain elusive. Pot trials were carried out including seven levels of P (0, 12.5, 25, 50, 100, 200 or 400 mg kg^-1) and non-mycorrhizal inoculation (NM), inoculation of Funneliformis mosseae (F.m) or Glomus versiforme (G.v). The present results found that grain phosphorus concentration increased with increase of P level from 0 to 100 mg kg^-1 and then tended to plateau, while grain Se concentration decreased with the level of P from 0 to 400 mg kg^-1. Based on mathematical modeling, inoculation of F.m or G.v dramatically improved grain Se concentration by 16.90% or 12.53% under the lower level of P (48.76 mg kg^-1). Furthermore, partial least squares path modeling (PLS-PM) identified that both up-regulated of the expression of AMF-inducible phosphate transporter and improved Se bioavailability in rhizosphere soil contributed to enhancing plant Se concentration under P levels ≤ 100 mg kg^-1. The present study demonstrated that AMF combined with 48.76 mg kg^-1 P applied in soil can not only achieve high grain yield, but also fully exploit the biological potential of Se uptake in wheat.

Chlorophyll fluorescence and grain filling characteristic of wheat (Triticum aestivum L.) in response to nitrogen application level

BACKGROUND

This study aims to understand the influence of chlorophyll fluorescence parameters on yield of winter wheat in some areas of China. Nitrogen (N) application is believed to improve photosynthesis in flag leaf ultimately increase final yield.

METHODS AND RESULTS

To understand the response of chlorophyll fluorescence parameters of wheat, flag leaf and the effect of N fertilization was carried out at booting stage under greenhouse during year 2018-2019 using winter wheat cultivar "Yunhan-20410' 'Yunhan-618". The results showed that the maximum chlorophyll content of flag leaves occurred at booting stage. Under, Yunhan-20410 condition, maximum photochemical quantum efficiency (FV/Fm), potential activity (ΦPSII), potential activity of PSII (FV/FO), and photochemical quenching coefficient (qp) showed "high-low" variation, and the maximum values were observed between May 4 and May 12. However, Yunhan-20410 showed FV/Fm, FV/FO, and qp showed "low-high-low" curve at booting stage. Compared to Yunhan-618, Yunhan-20410 at booting stage significantly decreased FV/Fm, FV/FO, qp, and ΦPSII (P<0.05), and non-photochemical quenching (NPQ) significantly increased (P<0.05).

CONCLUSION

The outcome of present investigation suggest that chlorophyll fluorescence parameters could be valuable insight to understand yield stability under stress condition. Moreover, the investigated parameters could be useful criteria for selection of genotypes under varying nitrogen application levels.

Monitoring seasonal and phenological variability of cover management factor for wheat cropping systems under semi-arid climate conditions

In modeling studies, the use of spatial data derived from geographic information systems and remote sensing applications to simulate the impact of phenological and seasonal changes on soil loss has a promising effect on the accuracy of predictions. The objective of this work was to estimate the C-factor (cover management) as a dynamic-factor RUSLE (revised universal soil loss equation) model based on an NDVI (Normalized Difference Vegetation Index) approach derived from high-resolution Landsat 8 and Landsat ETM7 satellite images for 140 different rain-fed wheat parcels in terms of seasonal and phenological-based by the integrated use of remote sensing and GIS. Overall, it was found that the highest C values, an average of 0.70, were estimated for the emergence period of the wheat, while the lowest value of 0.06 was found in the booting period. Seasonally, the estimated average C values in these parcels were 0.69, 0.63, 0.13, and 0.44 for the autumn, winter, spring, and summer, respectively. Corresponding soil losses for those seasons were 1.70, 1.55, 0.28, and 1.13 t ha^-1 year^-1 respectively. Comparatively, without considering the phenological growing periods of wheat, the annual predicted soil loss rate was 11.5% higher than the conditions considered. The present study concluded that an assessment of seasonal and phenological changes in the C-factor for fragile ecosystems with weak crop-cover development could significantly improve the accuracy of the RUSLE model predictions and effectively manage limited soil and water resources.

Predicting yellow rust in wheat breeding trials by proximal phenotyping and machine learning

BACKGROUND

High-throughput plant phenotyping (HTPP) methods have the potential to speed up the crop breeding process through the development of cost-effective, rapid and scalable phenotyping methods amenable to automation. Crop disease resistance breeding stands to benefit from successful implementation of HTPP methods, as bypassing the bottleneck posed by traditional visual phenotyping of disease, enables the screening of larger and more diverse populations for novel sources of resistance. The aim of this study was to use HTPP data obtained through proximal phenotyping to predict yellow rust scores in a large winter wheat field trial.

RESULTS

The results show that 40-42 spectral vegetation indices (SVIs) derived from spectroradiometer data are sufficient to predict yellow rust scores using Random Forest (RF) modelling. The SVIs were selected through RF-based recursive feature elimination (RFE), and the predicted scores in the resulting models had a prediction accuracy of r_s = 0.50-0.61 when measuring the correlation between predicted and observed scores. Some of the most important spectral features for prediction were the Plant Senescence Reflectance Index (PSRI), Photochemical Reflectance Index (PRI), Red-Green Pigment Index (RGI), and Greenness Index (GI).

CONCLUSIONS

The proposed HTPP method of combining SVI data from spectral sensors in RF models, has the potential to be deployed in wheat breeding trials to score yellow rust.

Increasing temperature during early spring increases winter wheat grain yield by advancing phenology and mitigating leaf senescence

High temperature usually reduces wheat yield, especially at critical growth stages, such as anthesis and grain filling. However, effects of increasing temperature during wintering period on winter wheat growth and development are rarely reported. Hence, this three-year field experiment evaluated how artificial warming during early spring (wintering period) affects winter wheat. The warming treatment (WT) advanced the wheat reviving, jointing, anthesis, and maturity stages, but the average temperature in each growing stage reduced, thus extending the duration of tillering, spike differentiation, and grain filling. Concurrently, the leaf area index and biomass accumulation were obviously increased. Additionally, WT showed a lower leaf senescence rate compared with that of control (CK). Also, the photosynthesis rate and SPAD of WT were increased relative to CK. WT increased superoxide dismutase and peroxidase activities, and reduced malondialdehyde content in flag leaf during the grain filling stage, suggesting WT during early spring could delay leaf senescence after anthesis, which contributed to a high filling rate and long filling duration. Correspondingly, the final spike number, kernel number, and kernel weight of WT were significantly increased compared with CK. In the three seasons, grain yield was increased by 18.2%-37.5% in WT compared with CK. Results of this study provided a new viewpoint that increasing temperature could shorten the wintering period but extend the effective growth phase, and increase grain yield in winter wheat.

Influence of arbuscular mycorrhizal fungi on selenium uptake by winter wheat depends on the level of selenate spiked in soil

Selenium (Se) deficiency has been a public health concern for years. Arbuscular mycorrhizal fungi (AMF) play an essential role in improving Se uptake in crops, but related mechanisms still remain unclear. To explore the influence of AMF on uptake of Se in winter wheat, a pot experiment was conducted to inoculate wheat with Funneliformis mosseae (F.m) or not under different levels of selenate in soil. The present results indicated that inoculation of F.m significantly (p < 0.05) increased Se concentration in shoots and roots of wheat under low level of selenate (≤5.0 mg kg^-1) treatments, while the contrary pattern was recorded under high level of selenate (15 and 20 mg kg^-1) treatments. Moreover, inoculation of F.m significantly increased concentration of available Se in soil by 4.68-34.05%. Under selenate ≤5 mg kg^-1 treatments, the expression of TaeSultr1;1 and TaeSultr1;3 in roots of mycorrhizal wheat was significantly up-regulated by 3.06-5.53 and 0.63-5.12 times, while reached saturation under selenate >5 mg kg^-1 treatments. In addition, partial least squares path modeling (PLS-PM) showed that inoculation of AMF directly affected the expression of sulfate transporter and that both sulfate transporter and soil Se fractions played a significant positive effect on plant Se content. The present study indicated that AMF on Se concentration in winter wheat depends on the level of selenate spiked in soil and added to our understanding of the functions and applications of AMF on crop Se absorption.

Size-dependent transformation, uptake, and transportation of SeNPs in a wheat-soil system

Foliar application of selenium nanoparticles (SeNPs) has been used to enhance Se concentration in winter wheat, but soil application of SeNPs on Se uptake in the crop and their transformation in soil are still limited. This study investigated the effects of varying sizes (50, 100, 200 nm) and concentrations (0, 2, 5, 25, 100 mg kg^-1) of chemical synthesized SeNPs in soil on uptake and accumulation of Se in the crop at maturity and related mechanisms. SeNPs not only posed very low toxic to plant growth, except for leaf, but also significantly enhanced grain Se concentration. Regardless of concentration of SeNPs added to soil, the transformation rate of the larger sized SeNPs (200 nm) in soil was significantly (p < 0.05) higher than that of the smaller one, which is mainly due to the latter was more easily adsorbed onto soil organic matter and reluctant to be oxidized. Significantly higher grain Se concentration under the larger sized SeNPs contributed to significantly higher transformation rate of SeNPs and concentration of available Se in soil. The present study showed that the larger sized SeNPs in soil had significant advantages including higher grain Se concentration and Se utilization efficiency for wheat Se biofortification.

Selenium inhibits cadmium uptake and accumulation in the shoots of winte wheat by altering the transformation of chemical forms of cadmium in soil

This study aimed to investigate the effects of selenium application on cadmium absorption, transport, and soil cadmium forms of winter wheat at different stages. A pot experiment with one Cd application (6 mg·kg^-1) and five Se application levels (0, 1, 2, 5, and 10 mg·kg^-1) was conducted. The results showed that Se application increased the grain yield of winter wheat, especially at 5 mg·kg^-1 under Cd stress. As Se was supplied at 5 (Se₅) and 10 (Se₁₀) mg·kg^-1, the Cd concentrations in roots and shoots, including stems, spikes, glumes, and grains, decreased at different growth stages, and the decreases in grain were 46.1% and 70.9% respectively. Se₅ and Se₁₀ also significantly decreased the translocation factors of Cd from roots to shoots, roots to stems, stems to spikes, and glumes to grains, promoted the accumulation of Cd in roots, and inhibited the accumulation of Cd in shoots and final grains at different growth stages, and the accumulation of Cd in grains decreased by 16.9% and 68.1%, respectively. High levels of Se application (Se₅ and Se₁₀) decreased the concentrations and proportions of exchangeable Cd (EXC-Cd) and iron (Fe)-manganese (Mn) oxide-bound Cd (R₂O₃-Cd) but increased the concentration and proportion of residual Cd (RES-Cd) in both soils with wheat and fallow soil at different growth stages. Therefore, under Cd stress, high levels of Se application reduced the shoot Cd concentration by inhibiting the uptake and transport of Cd from roots to shoots, and decreased the bioavailability of Cd in both soil with wheat and fallow by enhancing the transformation and distribution of RES-Cd from EXC-Cd and R₂O₃-Cd.

Time-course transcriptome profiling revealed the specific expression patterns of MADS-box genes associated with the distinct developmental processes between winter and spring wheat

The shoot apex is a region where new cells are produced and elongate. The developmental state of the wheat shoot apex under low temperature affects its cold resistance. In this study, the morphology of shoot apex before overwintering was characterized for 24 wheat line with different winter and spring characteristics. Our research showed that the shoot apex of autumn-sown spring wheat lines reached the temperature sensitive double-ridge stage before overwintering, whereas shoot apex of winter wheat lines are found in temperature-insensitive vegetative or elongation stages. In order to explore how gene expression is associated with shoot apex differentiation in winter and spring wheat, we used strand-specific RNA sequencing to profile the gene expression patterns at four time-points between 14 after germination and 45 days after germination in the winter wheat cultivar Dongnongdongmai No. 1 (DM1) and in the spring wheat cultivar China Spring (CS). We identified 11,848 differentially expressed genes between the two cultivars. Most up-regulated genes in CS were involved in energy metabolism and transport during the seedling stage, whereas up-regulated genes in DM1 were involved in protein and DNA synthesis. MADS-box genes affect plant growth and development. In this study, MADS-boxes with differential expression between CS and DM1 were screened and evolutionary tree analysis was conducted. During all sampling periods, CS highly expressed MADS-box genes that induce flowering promotion genes such as VRN1, VRT and AG, while lowly expressed MADS-box genes that induce flowering-inhibiting homologous genes such as SVP. TaVRN1 composition in DM1 and CS was vrn-A1, vrn-B1, and Vrn-D1b. Analysis of the sequence of TaVRN1 (TraesCS5A01G391700) from DM1 and CS revealed 5 SNP differences in the promoter regions and 3 SNP deletions in the intron regions. The expression levels of cold resistant genes in DM1 were significantly higher than those in CS at seedling stage (neither DM1 nor CS experienced cold in this study), including CBF, cold induced protein,acid desaturase and proline rich proteins. Additionally, the expression levels of auxin-related genes were significantly higher in CS than those in DM1 at 45 days after germination. Our study identified candidate genes associated with the process of differentiation of the shoot apex in winter and spring wheat at the seedling stage and also raised an internal stress tolerance model for winter wheat to endogenously anticipate the coming stressful conditions in winter.

Effects of fallow tillage on winter wheat yield and predictions under different precipitation types

In northern China, precipitation that is primarily concentrated during the fallow period is insufficient for the growth stage, creates a moisture shortage, and leads to low, unstable yields. Yield prediction in the early growth stages significantly informs field management decisions for winter wheat (Triticum aestivum L.). A 10-year field experiment carried out in the Loess Plateau area tested how three tillage practices (deep ploughing (DP), subsoiling (SS), and no tillage (NT)) influenced cultivation and yield across different fallow periods. The experiment used the random forest (RF) algorithm to construct a prediction model of yields and yield components. Our results revealed that tillage during the fallow period was more effective than NT in improving yield in dryland wheat. Under drought condition, DP during the fallow period achieved a higher yield than SS, especially in drought years; DP was 16% higher than SS. RF was deemed fit for yield prediction across different precipitation years. An RF model was developed using meteorological factors for fixed variables and soil water storage after tillage during a fallow period for a control variable. Small error values existed in the prediction yield, spike number, and grains number per spike. Additionally, the relative error of crop yield under fallow tillage (5.24%) was smaller than that of NT (6.49%). The prediction error of relative meteorological yield was minimum and optimal, indicating that the model is suitable to explain the influence of meteorological factors on yield.

Temporal expression study of miRNAs in the crown tissues of winter wheat grown under natural growth conditions

BACKGROUND

Winter wheat requires prolonged exposure to low temperature to initiate flowering (vernalization). Shoot apical meristem of the crown is the site of cold perception, which produces leaf primordia during vegetative growth before developing into floral primordia at the initiation of the reproductive phase. Although many essential genes for winter wheat cold acclimation and floral initiation have been revealed, the importance of microRNA (miRNA) meditated post-transcriptional regulation in crowns is not well understood. To understand the potential roles of miRNAs in crown tissues, we performed a temporal expression study of miRNAs in crown tissues at the three-leaf stage, winter dormancy stage, spring green-up stage, and jointing stage of winter wheat grown under natural growth conditions.

RESULTS

In total, 348 miRNAs belonging to 298 miRNA families, were identified in wheat crown tissues. Among them, 92 differentially expressed miRNAs (DEMs) were found to be significantly regulated from the three-leaf stage to the jointing stage. Most of these DEMs were highly expressed at the three-leaf stage and winter dormancy stage, and then declined in later stages. Six DEMs, including miR156a-5p were markedly induced during the winter dormancy stage. Eleven DEMs, including miR159a.1, miR390a-5p, miR393-5p, miR160a-5p, and miR1436, were highly expressed at the green-up stage. Twelve DEMs, such as miR172a-5p, miR394a, miR319b-3p, and miR9676-5p were highly induced at the jointing stage. Moreover, 14 novel target genes of nine wheat or Pooideae-specific miRNAs were verified using RLM-5' RACE assay. Notably, six mTERFs and two Rf1 genes, which are associated with mitochondrial gene expression, were confirmed as targets of three wheat-specific miRNAs.

CONCLUSIONS

The present study not only confirmed the known miRNAs associated with phase transition and floral development, but also identified a number of wheat or Pooideae-specific miRNAs critical for winter wheat cold acclimation and floral development. Most importantly, this study provided experimental evidence that miRNA could regulate mitochondrial gene expression by targeting mTERF and Rf1 genes. Our study provides valuable information for further exploration of the mechanism of miRNA mediated post-transcriptional regulation during winter wheat vernalization and inflorescent initiation.

Genetic dissection of grain architecture-related traits in a winter wheat population

BACKGROUND

The future productivity of wheat (T. aestivum L.) as the most grown crop worldwide is of utmost importance for global food security. Thousand kernel weight (TKW) in wheat is closely associated with grain architecture-related traits, e.g. kernel length (KL), kernel width (KW), kernel area (KA), kernel diameter ratio (KDR), and factor form density (FFD). Discovering the genetic architecture of natural variation in these traits, identifying QTL and candidate genes are the main aims of this study. Therefore, grain architecture-related traits in 261 worldwide winter accessions over three field-year experiments were evaluated.

RESULTS

Genome-wide association analysis using 90K SNP array in FarmCPU model revealed several interesting genomic regions including 17 significant SNPs passing false discovery rate threshold and strongly associated with the studied traits. Four of associated SNPs were physically located inside candidate genes within LD interval e.g. BobWhite_c5872_589 (602,710,399 bp) found to be inside TraesCS6A01G383800 (602,699,767-602,711,726 bp). Further analysis reveals the four novel candidate genes potentially involved in more than one grain architecture-related traits with a pleiotropic effects e.g. TraesCS6A01G383800 gene on 6A encoding oxidoreductase activity was associated with TKW and KA. The allelic variation at the associated SNPs showed significant differences betweeen the accessions carying the wild and mutated alleles e.g. accessions carying C allele of BobWhite_c5872_589, TraesCS6A01G383800 had significantly higher TKW than the accessions carying T allele. Interestingly, these genes were highly expressed in the grain-tissues, demonstrating their pivotal role in controlling the grain architecture.

CONCLUSIONS

These results are valuable for identifying regions associated with kernel weight and dimensions and potentially help breeders in improving kernel weight and architecture-related traits in order to increase wheat yield potential and end-use quality.

Agronomical traits associated with yield and yield components of winter wheat as affected by nitrogen managements

Nitrogen fertilizer is one of the key elements to increase the yield and significance of winter wheat. The experiment was established in the split zone design and was repeated three times. The nitrogen application level is set to 4 treatments, 75, 150, 225 and 300 kg ha-1 are arranged in the main plot, and different nitrogen application ratios are arranged in the sub-plots, respectively 5:5 (50%+50%) and 6: 4 (60%) + 40%). Nitrogen fertilizer was applied before sowing, jointing stage, flowering stage and filling stage. The experimental plot is 12 m2 (3 m × 4 m). The results showed that under the conditions of 225 kg/hm2 nitrogen application and 60%+40% nitrogen application rate, the yield of Jintai 182 was the highest compared with other treatment groups. With the increase of nitrogen application rate, the number of ears, grains per ear, thousand-grain weight and grain yield all increase first and then decrease. Each factor reached the highest 225 N kg / hm2, 417.17, 30.74, 40.96 g and 6182.11 kg / hm2. Compared with 75 kg/hm2 topdressing fertilizer, 225 kg/hm2 is a more suitable nitrogen fertilizer application rate for winter wheat. Within a reasonable range of nitrogen fertilizer application, there is a significant positive correlation between nitrogen content and winter wheat yield. By studying the amount of nitrogen fertilizer and a reasonable ratio of base fertilizer to topdressing, the utilization rate of nitrogen fertilizer can be maximized and excessive application of nitrogen fertilizer can be avoided.

Life cycle assessment of a long-term multifunctional winter wheat-summer maize rotation system on the North China Plain under sustainable P management

In sustainable agriculture, sufficient crop yields and nutrients must be produced while maintaining environmental protection. Considering the role of phosphorus (P) fertilizer in influencing crops yield and environmental security, life cycle assessment was used to examine the environmental impacts of long-term P application on the grain yield and nutritional quality of winter wheat and summer maize. Thus, a long-term field experiment with six P application rates for winter wheat (0, 25, 50, 100, 200, and 400 kg P ha^-1) and summer maize (0, 12.5, 25, 50, 100, and 200 kg P ha^-1) was conducted on the North China Plain (NCP). The results showed that the cradle-to-farm gate eutrophication potential (EP), energy depletion (ED), and P depletion (PD) were significantly affected by the P application rate applied in winter wheat and summer maize production. The critical P rate required to ensure food security for wheat and maize was in line with the optimal rate for sustainable environmental development in terms of grain production and nutrient levels. On the NCP, the ED and PD of summer maize with optimized P management over 10 years were less than those of winter wheat regardless of using yield or nutrient level as the functional unit. However, the EP of the nutrient supply in winter wheat was less than that in summer maize under optimized P fertilization. The specific nutritional components that limited improvements in environment of wheat and maize production under the optimal P rate were energy (calories) and protein, respectively. In conclusion, in a multifunctional winter wheat-summer maize rotation system, optimized P fertilization (50 kg ha^-1 for winter wheat and 25 kg ha^-1 for summer maize) combined with the planting of high-yield wheat varieties and high-protein maize varieties showed great potential to reduce the environmental impacts of wheat and maize production.

Leaf area index estimation model for UAV image hyperspectral data based on wavelength variable selection and machine learning methods

BACKGROUND

To accurately estimate winter wheat leaf area index (LAI) using unmanned aerial vehicle (UAV) hyperspectral imagery is crucial for crop growth monitoring, fertilization management, and development of precision agriculture.

METHODS

The UAV hyperspectral imaging data, Analytical Spectral Devices (ASD) data, and LAI were simultaneously obtained at main growth stages (jointing stage, booting stage, and filling stage) of various winter wheat varieties under various nitrogen fertilizer treatments. The characteristic bands related to LAI were extracted from UAV hyperspectral data with different algorithms including first derivative (FD), successive projections algorithm (SPA), competitive adaptive reweighed sampling (CARS), and competitive adaptive reweighed sampling combined with successive projections algorithm (CARS_SPA). Furthermore, three modeling machine learning methods including partial least squares regression (PLSR), support vector machine regression (SVR), and extreme gradient boosting (Xgboost) were used to build LAI estimation models.

RESULTS

The results show that the correlation coefficient between UAV and ASD hyperspectral data is greater than 0.99, indicating the UAV data can be used for estimation of wheat growth information. The LAI bands selected by using different algorithms were slightly different among the 15 models built in this study. The Xgboost model using nine consecutive characteristic bands selected by CARS_SPA algorithm as input was proved to have the best performance. This model yielded identical results of coefficient of determination (0.89) for both calibration set and validation set, indicating a high accuracy of this model.

CONCLUSIONS

The Xgboost modeling method in combine with CARS_SPA algorithm can reduce input variables and improve the efficiency of model operation. The results provide reference and technical support for nondestructive and rapid estimation of winter wheat LAI by using UAV.

Tillage systems as a function of greenhouse gas (GHG) emission and fuel consumption mitigation

In order to investigate the possibility of reducing GHG in winter wheat production, field trial was set up in a 3-year experiment (VS) with four different tillage systems (TS) and three N fertilization norms (FN). The tillage systems were CT-conventional tillage, DT-disk harrowing, LT-soil loosening, and NT-no tillage system. N fertilization norms were set to 120, 150 and 180 kg ha^-1. Fuel consumption was measured with three-channel valve, and total value of consumption was calculated on total machinery passes according to technological map. Calculation of greenhouse gas (GHG) emissions from winter wheat production were done by BioGrace model (version 4d 2015). GHG emission per ton of yearly raw material was calculated from fertilizers (production and field emissions), seed, plant protection and diesel usage, so the result was expressed in kg CO_2eq ha^-1 per year. The main properties of research (TS, FN and VS) are showing statistical significance on total GHG emission from winter wheat production. The largest GHG emission had LT tillage system with 261.89 kg CO_2eq ha^-1 from fuel emission and 2919.22 kg CO_2eq ha^-1 in total. This tillage system also had highest yield of 7.78 t ha^-1. The lowest yield was observed at NT system (6.92 t ha^-1), also with the lowest GHG emission from fuel consumption and total production (fuel 118.30 and total 2685.94 kg CO_2eq ha^-1). Reduced tillage system such as DT can significantly reduce GHG emissions from diesel consumption without having an impact on wheat yield. This study suggests that DT, primarily, and NT can be recommended as convenient agricultural practices conducive to reconstruct an optimal balance between GHG emissions, yields, and N excesses.

Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase genes of winter wheat enhance the cold tolerance of transgenic Arabidopsis

In this study, winter wheat G6PDH (TaG6PDH) and 6PGDH (Ta6PGDH) were investigated. Both their expression and their activity were upregulated under cold stress, suggesting that TaG6PDH and Ta6PGDH positively respond to cold stress in winter wheat. Exogenous abscisic acid (ABA) treatment markedly increased the expression and activity levels of TaG6PDH and Ta6PGDH in winter wheat under cold stress. Subsequently, TaG6PDH-and Ta6PGDH were overexpressed in Arabidopsis, and showed stronger reactive oxygen species (ROS)-scavenging ability and higher survival rate compared with wild-type (WT) plants under cold stress. In addition, we found that TaG6PDH and Ta6PGDH overexpression can promote the oxidative pentose phosphate pathway (OPPP) in the cytoplasm and peroxisomes of Arabidopsis. In summary, Arabidopsis overexpressing TaG6PDH and Ta6PGDH showed improved cold tolerance.

Comparison of new hyperspectral index and machine learning models for prediction of winter wheat leaf water content

BACKGROUND

The leaf water content estimation model is established by hyperspectral technology, which is crucial and provides technical reference for precision irrigation.

METHODS

In this study, two consecutive years of field experiments (different irrigation times and seven wheat varieties) in 2018-2020 were performed to obtain the canopy spectra reflectance and leaf water content (LWC) data. The characteristic bands related to LWC were extracted from correlation coefficient method (CA) and x-Loading weight method (x-Lw). Five modeling methods, spectral index and four other methods (Partial Least-Squares Regression (PLSR), Random Forest Regression (RFR), Extreme Random Trees (ERT), and K-Nearest Neighbor (KNN)) based characteristic bands, were employed to construct LWC estimation models.

RESULTS

The results showed that the canopy spectral reflectance increased with the increase of irrigation times, especially in the near-infrared band (750-1350 nm). The prediction accuracy of the newly developed differential spectral index DVI (R1185, R1307) was higher than that of the existing spectral index, with R² of 0.85 and R² of 0.78 for the calibration and validation, respectively. Due to a large amount of hyperspectral data, the correlation coefficient method (CA) and x-Loading weight (x-Lw) were used to select the water characteristic bands (100 and 28 characteristic bands, respectively) from the full spectrum. We found that the accuracy of the model based on the characteristic bands was not significantly lower than that of the full spectrum-based models. Among these models, the ERT- x-Lw model performed the best (R² and RMSE of 0.88 and 1.46; 0.84 and 1.62 for the calibration and validation, respectively). In addition, the accuracy of the LWC estimation model constructed by ERT-x-Lw was higher than that of DVI (R1185, R1307).

CONCLUSION

The two models based on ERT-x-Lw and DVI (R1185, R1307) can effectively predict wheat leaf water content. The results provide a technical reference and a basis for crop water monitoring and diagnosis under similar production conditions.

Resistance of winter wheat varieties to tan spot in the North Caucasus region of Russia

Tan spot caused by Pyrenophora tritici-repentis (Died.) Drechsler, in recent years, occupies an increasingly large area on the territory of Russia. Due to the wide distribution and economic significance of this disease, the search for resistant plants to the pathogen is relevant. This paper presents the results of a field assessment for 2017–2019 of 34 regionally distributed winter wheat varieties of Russian selection for resistance to P. tritici-repentis in the North Caucasus region of Russia. Field resistance - the development of the disease up to 30% against the background of artificial infection for three years was shown by 20.5% of the studied varieties. Wheat varieties were assessed for resistance to isolates of tan spot identified as races 1, 3, and 4 in the greenhouse at the seedling stage. The number of resistant accessions for each race was different and ranged from 12 to 20. The 12 varieties showed resistance to race 1, 14 varieties to race 3, 20 varieties to race 4. This research showed that the resistance to tan spot of studied varieties was race-specific. A functional allele of the susceptibility gene Tsn1 to P. tritici-repentis isolates, producing the toxin Ptr ToxA, was diagnosed by PCR method. Of the analyzed 34 varieties, 13 had a dominant allele of the Tsn1 (Tsn1⁺), and 21 had a recessive allele in the tsn1tsn1 homozygous state. All Tsn1⁺ varieties, and most varieties with recessive alleles tsn1tsn1, were susceptible to tan spot in the field. Varieties Dolya, Gurt, Lebed and Sila, which showed field resistance, had the tsn1tsn1 genotype. The expected reaction of varieties with different allelic composition of the Tsn1 gene to inoculation with the isolate of race 1, according to the generally accepted model of “gene-to-gene” interaction, did not coincide with that observed in reality, which confirms the results obtained by other authors. Research results demonstrate the effect of weather conditions on the susceptibility of wheat varieties to tan spot. In years with higher humidity and higher average air temperatures, the susceptibility response to the disease was observed in more varieties than in drier years. The studies show that the main part (79.5%) of winter wheat varieties of Russian selection widely zoned in the North Caucasus region of Russia are susceptible to P. tritici-repentis. Varieties that have been resistant to the pathogen in the adult phase in the field for three years and to the pathogen races in which the recessive allele of the tsn1 gene has been identified may be of interest as sources of resistance for developing new disease-resistant varieties.

First report of Heterodera filipjevi on winter wheat from Hebei Province in North China

Three of the cereal cyst nematodes, Heterodera avenae, H. filipjevi and H. latipons are considered to be the most economically important cyst nematodes that affect cultivated cereals around the world. H. filipjevi was first detected in China from Xuchang, Henan Province in 2010 (Peng et al. 2010) and now has been recorded in the Central China of Henan, Shandong and Anhui provinces and the Northwest China of Xinjiang Uygur Autonomous Region (Cui et al. 2020). In June 2019, 42 samples consisting of roots and soil were collected from winter wheat fields in Hebei Province of North China. Cysts were detected in 37 soil samples with a mean of 6.4 ± 1.67 cysts per 100 ml of soil. Cysts and second-stage juveniles (J2s) were extracted from root and soil following Cobb's sieving gravity method. Morphological and molecular studies of J2s and cysts confirmed its identity with H. filipjevi in 5 samples from Handan (N36°10'052" and E114°35'056"; N36°37'054" and E114°22'052"), Xingtai (N36°53'060" and E114°30'011") and Shijiazhuang (N 37°26'048" and E 116°05'039") in Hebei Province, China. Morphologically, the cysts are lemon-shaped, light or dark brown in color. The vulval cone is bifenestrate with horseshoe-shaped semifenestrae, strongly globular bullae, and well-developed underbridge. Measurements (mean +_ sd (range)) of cysts (n=10), body length not including neck is 743.0 ± 36.1 μm (665 - 780 μm), body width is 559.0 ± 50.0 μm (455 - 639 μm), length / width ratio is 1.33 ± 0.07 (1.20 - 1.46); neck length is 99.3 ± 8.8 μm (85 - 122 μm); fenestrae length is 56.8 ± 5.0 μm (49 - 65 μm) and width is 25.5 ± 1.8 μm (21.1 - 27.8 μm); underbridge length is 84.0 ± 8.1 μm (62 - 93 μm); and vulval slit length is 8.6 ± 0.5 μm (7.2 - 9.1 μm). Measurements of J2s (n = 12), body length is 541 ± 11.4 μm (490 - 578 μm); stylet length is 22.3 ± 0.5 μm (22.0 - 25.0 μm) with anchor-shaped basal knobs; tail length is 57.7 ± 3.7 μm (52.7 - 65.2 μm), and hyaline tail terminal length is 36.5 ± 2.8 μm (32 - 39.8 μm). The tail had a sharp terminus. Morphology of the cysts and J2s were consistent with the record of H. filipjevi (Peng et al. 2010; Subbotin et al. 2010). The amplifications of rDNA-internal transcribed spacer (ITS) fragments were generated with a PCR fragment of 1054 bp from single cysts of each population, using primers TW81 and AB28 (Joyce et al. 1994). The PCR tests for each sample were repeated five times. The PCR product was purified and sequenced. All nucleotide sequences of ITS-rDNA were submitted to GenBank under accession numbers MW282843-6. Sequences from the ITS region were more than 99.5% identical to those of H. filipjevi from Egypt (KF225725), Turkey (KR704308, KR704293 and MN848333) and China (KT314234, MT254744 and KY448473). These results from ITS supported its identity as H. filipjevi. The results were also confirmed by species specific sequence characterized amplified region primers of H. filipjevi (Peng et al. 2013). Pathogenicity of the H. filipjevi was confirmed by infection of winter wheat (Triticum aestivum L cv. 'Aikang58') and examination of the nematode development and reproduction. Wheat seeds were germinated in petri dishes and then transplanted into five polyvinyl chloride tubs (3 cm in diameter, 25 cm in length) that contained 150 cm3 of a sterile soil mixture (loamy soil: sand = 1:1), each with 5 cysts (mean of 252.0 eggs/cyst). Plants were grown in an artificial climate box for one week at 14/18°C, two weeks at 16/20°C, five weeks at 18/25°C and two weeks at 22/30°C, under 8 h of darkness/16 h light and normal culturing practices (Cui et al. 2015). The parasitic J2s, third and fourth-stage juveniles, and adult females were observed in roots stained with acid fuchsin at 10, 20, 30, and 50 days after inoculation (DAI), and an average of 32.0 cysts per tubes were extracted 70 DAI. The new cyst' morphological and molecular characteristics were identical to the H. filipjevi cysts from the original soil samples. Three other tubes without cysts were set as control and there were no newly formed cysts. Heterodera avenae and H. filipjevi had been detected in a total of 16 wheat-producing provinces in China, which resulted in losses of 1.9 billion CNY year-1 (Cui et al. 2015). To our knowledge, this is the first report of H. filipjevi in Hebei Province of North China. Cereal cyst nematodes are easily transferred to non-infested areas by many avenues, resulting in increased species and pathotype complexity (Cui et al. 2020). Once H. filipjevi continues to spread in main wheat producing area of China, it could become be a new threat to cereals production. It is time to take effective control methods to prevent H. filipjevi further dispersal, especially through the farming machinery transmission. Hebei Province is one of the most important major grain-producing areas, our findings will be very beneficial for H. filipjevi management and further research on winter wheat in Hebei Province, North China.

Clisagri: An R package for agro-climate services

Crop yields are affected by unfavourable/extreme weather and climate events occurring during sensitive growth stages. Understanding the risks associated with these events is essential to adapt agro-management decisions and reduce losses. For this purpose, we propose a targeted climate service integrating a dynamic crop phenology model with an approach based on dedicated agro-climate risk indicators. The initial set of these indicators has been developed in a co-design approach with agronomists and durum wheat farmers participating as end-users in the H2020-MedGOLD project. Four groups of indicators characterize drought events, excessive wetness, cold stress and heat stress during sensitive growth stages. The proposed approach has been fully implemented as an R-package named Clisagri. The package is complemented with a set of optimization functions, which target optimal variety selection in terms of crop cycle duration.

Belowground fungal community diversity, composition and ecological functionality associated with winter wheat in conventional and organic agricultural systems

Understanding the impacts of agricultural practices on belowground fungal communities is crucial in order to preserve biological diversity in agricultural soils and enhance their role in agroecosystem functioning. Although fungal communities are widely distributed, relatively few studies have correlated agricultural production practices. We investigated the diversity, composition and ecological functionality of fungal communities in roots of winter wheat (Triticum aestivum) growing in conventional and organic farming systems. Direct and nested polymerase chain reaction (PCR) amplifications spanning the internal transcribed spacer (ITS) region of the rDNA from pooled fine root samples were performed with two different sets of fungal specific primers. Fungal identification was carried out through similarity searches against validated reference sequences (RefSeq). The R package ‘picante’ and FUNGuild were used to analyse fungal community composition and trophic mode, respectively. Either by direct or cloning sequencing, 130 complete ITS sequences were clustered into 39 operational taxonomic units (OTUs) (25 singletons), belonging to the Ascomycota (24), the Basidiomycota (14) and to the Glomeromycota (1). Fungal communities from conventional farming sites are phylogenetically more related than expected by chance. Constrained ordination analysis identified total N, total S and Pcal that had a significant effect on the OTU’s abundance and distribution, and a further correlation with the diversity of the co-occurring vegetation could be hypothesised. The functional predictions based on FUNGuild suggested that conventional farming increased the presence of plant pathogenic fungi compared with organic farming. Based on diversity, OTU distribution, nutrition mode and the significant phylogenetic clustering of fungal communities, this study shows that fungal communities differ across sampling sites, depending on agricultural practices. Although it is not fully clear which factors determine the fungal communities, our findings suggest that organic farming systems have a positive effect on fungal communities in winter wheat crops.

The Environmental Degradation and Distribution of Saflufenacil, a Fluorinated Protoporphyrinogen IX Oxidase-Inhibiting Herbicide, on a Canadian Winter Wheat Field

Saflufenacil when applied to a field is susceptible to transport, degradation, and transformation. We used a laboratory-based approach to model the fate of saflufenacil in the environment, the results of which are compared directly with those observed in a field study where saflufenacil was applied to a crop of winter wheat at a standard rate of 63 g of active ingredient/hectare. The water solubility of 2.1 g/L for saflufenacil allows for vertical transport through soil at a rate of 4.3 cm/mL of rainwater, and a soil adsorption coefficient K_OC of 28.8 suggests that some of the herbicide will absorb to the soil. Of the saflufenacil in the soil, 78 ± 2.1% (n = 18) partitioned into plants, including nontargeted crop species, where it was found primarily in leaves (78 ± 2.1%, n = 18) and roots (22 ± 1.7%, n = 18). The saflufenacil that does not partition into plants or undergo vertical transport followed a degradation pathway into 3 metabolites: a uracil-ring N-demethylated metabolite (Saf-µCH₃ ), a doubly N-demethylated metabolite (Saf-2CH₃ ), and a ring-cleavage metabolite (Saf-RC), identified using nontargeted mass spectrometry. In the field, saflufenacil was observed to degrade over 212 d to the persistent metabolite Saf-RC. This metabolite was found at a concentration that was 1/10th of that applied to the field, suggesting that the majority of saflufenacil had undergone transport through the soil, or uptake into the winter wheat crop. Field samples were further examined using F-19 nuclear magnetic resonance and nontargeted mass spectrometry to rule out the potential of other degradation products. Environ Toxicol Chem 2020;39:1918-1928. © 2020 SETAC.

Dynamic distribution and accumulation of PAHs in winter wheat during whole plant growth: Field investigation

A field investigation was conducted to study the dynamic distribution and accumulation of polycyclic aromatic hydrocarbons (PAHs) in winter wheat in the surrounds of a coal-fired power plant. During March to June 2019, various tissues of winter wheat and the corresponding rhizosphere soil were collected for determination of PAHs. A clear spatial downward trend was found in concentration of Σ₁₅PAHs in rhizosphere soil and wheat grain (194-237 μg kg^-1 DM) with the increasing distance from the coal-fired power plant. Moreover, Σ₁₅PAHs concentration in rhizosphere soil (1081 μg kg^-1 DM), root (464 μg kg^-1 DM) and stem (365 μg kg^-1 DM) of winter wheat at regreening stage and leaf (323 μg kg^-1 DM) at anthesis stage were significantly (p < 0.001) higher than that (895, 432, 287 and 265 μg kg^-1 DM) at maturity stage, respectively. From regreening to maturity stage, root concentration factors (RCF) of 3- and 4-ring PAHs exhibited an increasing trend but the 5-ring PAHs showed an apparently downward trend. However, stem concentration factors (SCF) of 3- and 4-ring PAHs showed a decrease trend while the 5- and 6-ring showed first down and then stable trend. There were positive linear relationship between logKow and logSCF at anthesis (r = 0.681, p < 0.05) and maturity stage (r = 0.751, p < 0.05). Based on linear regression analysis, PAHs in grain mainly came from the transfer of vegetative tissues, and the contribution of PAHs from stem and leaf to grain was higher than that from root. In addition, the present study also found that the physicochemical properties of PAHs play a crucial role in transfer of PAHs from root to vegetative tissues and then to grain. The present research provided more comprehensive information on the fate of PAHs in winter wheat and the safety of the agricultural products.

MicroRNA and regulation of auxin and cytokinin signalling during post-mowing regeneration of winter wheat (Triticum aestivum L.)

Winter wheat not only provides adequate fresh forage grass in winter, but also ensures ample grain production in summer. The mechanisms underlying the regeneration of winter wheat after mowing or grazing are not well understood. In this study, the miRNA expression profile of winter wheat was determined using RNA sequencing and the endogenous auxin and cis-zeatin concentrations, as well as the expression of related miRNA-targeted genes, were measured. During the post-mowing regeneration of winter wheat, the concentrations of endogenous indole-3-acetic acid (IAA), methyl indole-3-acetate (ME-IAA), and indole-3-carboxaldehyde (ICA) decreased, while those of cis-zeatin (cZ) increased. Moreover, 15 novel miRNAs and three known miRNAs were found to be involved in the synthesis and signalling transduction of auxins and cytokinins (CKs). Among these miRNAs, miR1153-y, miR5059-x, miR2916-x, novel-miR1532-3p, novel-miR1060-3p, and novel-miR0890-3p, were found to be negatively correlated with the expression of their target genes including auxin response GH3.7, auxin response factor (ARF), type-A two-component response regulator (A-ARR), aldehyde dehydrogenase (ALDH), and O-glucosyltransferase (CISZOG). Furthermore, miR1153-y was identified as mediating the cleavage of GH3.7 by RACE assay. In turn, these genes inhibited the biosynthesis and signalling of IAA and activated CK signal transduction, resulting in the rapid regeneration of mowed winter wheat. This study revealed that some miRNAs exert a positive regulatory effect on the post-mowing regeneration of winter wheat by controlling the synthesis and signal transduction of IAA and CK, and our founding will aid developments in biotechnology aimed at improving the post-mowing regeneration ability of winter wheat.

Carbon emission and water use efficiency response to tillage methods and planting patterns of winter wheat in the North China Plain

Background

Implementing sustainable farming practices for winter wheat (Triticum aestivum L.) in the North China Plain may be a way to reduce carbon emissions. No tillage generally results in less net CO₂ loss from farmland, but no tillage also reduces the grain yield and water use efficiency (WUE) of winter wheat. Wide-precision planting of winter wheat may enhance the grain yield and WUE; however, it is not known precisely how tillage and planting patterns affect CO₂ exchange, grain yield and WUE.

Methods

In this study, two tillage methods (conventional tillage, T and no tillage, NT) and two planting patterns (conventional planting, C and wide-precision planting, W) were used in two consecutive winter wheat growing seasons.

Results

Compared with the T treatments, the NT treatments had significantly lower cumulative net CO₂ emissions in 2015–2016 and 2016–2017 (30.8 and 21.3%, respectively), and had lower grain yields (9.0 and 9.4%, respectively) and WUE (6.0 and 7.2%, respectively). The W treatments had a compensating effect on grain yield failure and reduced cumulative net CO₂ emissions more than C treatments, thereby increasing WUE, reducing carbon emissions per unit water consumption, and increasing the yield carbon utilization efficiency (YCUE). The lowest cumulative CO₂ emissions and highest YCUE were observed for NT with W treatment. Results from this analogous tillage experiment indicated that NT and W farming practices provide an option for reducing carbon emissions and enhancing WUE and YCUE for sustainable winter wheat development.

Estimation of nitrogen supply for winter wheat production through a long-term field trial in China

Excessive synthetic nitrogen (N) applications, high mineral N accumulation and low N use efficiency (NUE) are current issues in intensively cultivated winter wheat production system impeding the sustainable development of agriculture in China. To solve these problems, soil accumulated N in the top 1 m of the soil profile before sowing (N_soil), returned straw-N from the previous maize crop (N_straw) and fertilizer N application (N_fertilizer) should be comprehensively considered N supply sources in N management. As such, the objective of this research was to determine the optimal total N supply (TN_supply) level needed to meet crop requirements while minimizing environmental impacts. A 9-year on-farm experiment was conducted in accordance with a split-plot design involving two different fertilizer management systems (main treatments) and three N application strategies (sub treatments). Extensive TN_supply levels (ranging from 61 kg ha^-1 to 813 kg ha^-1) were detected, and relative yield (RY), N input and N output in response to the TN_supply were measured. The relationships between TN_supply and RY, N input, and N output strongly fit linear-plateau, linear, and linear-plateau models, respectively. The minimum TN_supply levels needed to achieve the maximum RY and N output were 325 and 392 kg ha^-1, respectively. On the basis of N supply capacity, the TN_supply was removed from the growing system by 61% (N input). As the N input increased past 209 kg ha^-1, the NUE declined, at which point the TN_supply reached 433 kg ha^-1. Therefore, the suitable TN_supply should range from 325 kg ha^-1 (ensuring a total N supply for high yield and N uptake) to 433 kg ha^-1 (obtaining a relatively higher NUE and less N loss to the environment). The TN_supply was highlighted to be an indicator for use in N management recommendations. Considering the average high N accumulation in winter wheat production systems, N management should essentially take into account the consumption of N_soil, the levels of N_straw and the minimum application of N_fertilizer to obtain high yields while minimizing environmental impacts under suitable TN_supply levels.

Impact of spring phenology variation on GPP and its lag feedback for winter wheat over the North China Plain

Spring green-up date (GUD) is a sensitive indicator of climate change, and of great significance to winter wheat production. However, our knowledge of the chain relationships among them is relatively weak. In this study, based on 8-day Enhanced Vegetation Index (EVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS) from 2001 to 2015, we first assessed the performance of four algorithms for extracting winter wheat GUD in the North China Plain (NCP). A multiple linear regression model was then established to quantitatively determine the contributions of the time lag effects of hydrothermal variation on GUD. We further investigated the interactions between GUD and gross primary production (GPP) comprehensively. Our results showed that the rate of change in curvature algorithm (RCCmax) had better performance in capturing the spatiotemporal variation of winter wheat GUD relative to the other three methods (Kmax, CRmax, and cumCRmax). Regarding the non-identical lag time effects of hydrothermal factors, hydrothermal variations could explain winter wheat GUD variations for 82.05% of all pixels, 36.78% higher than that without considering the time lag effects. Variation in GUD negatively correlated with winter wheat GPP after green up in most parts of the NCP, significantly in 35.75% of all pixels with a mean rate of 1.89 g C m^-2 yr^-1 day^-1. Meanwhile, winter wheat GPP exerted a strongly positive feedback on GUD in >82.42% of all pixels (significant in 28.01% of all pixels), characterized by a humped-shape pattern along the long-term average plant productivity. This finding highlights the complex interaction between spring phenology and plant productivity, and also suggests the importance of preseason climate factors on spring phenology.

Soil water deficit promotes the effect of atmospheric water deficit on solar-induced chlorophyll fluorescence

Solar-induced chlorophyll fluorescence (SIF) is a novel optical signal that has been successfully used to track plant dynamics with the influence of soil water deficit. However, the effect of atmospheric water deficit on SIF under the impact of soil water deficit still remains unclear. Here, continuous measurements of SIF (at 760 nm, F760) of winter wheat under different soil water deficit were collected with a self-developed system. Additionally, soil moisture and atmosphere parameters [including air temperature (Ta), relative air humidity (Rh), and photosynthetically active radiation at 400-700 nm (PAR)] were also synchronously collected by common commercial devices. Vapor pressure deficit (VPD) was calculated based on the measurements of Ta and Rh. The results showed that the driving effect of PAR on F760 was obvious as we expected. Additionally, such effects of PAR on AF760 (F760/PAR) and Fy760 (F760/L685, L685 was canopy radiance at 685 nm) still existed when the PAR influences were partially removed by the calculation of F760/PAR and F760/L685. Furthermore, the relationship of PAR with AF760 or Fy760 was observed to be strengthened under the situation of water deficit through the analysis of Pearson correlations. With the influence of PAR, the accelerative effect of VPD on SIF under soil water deficit was not always observed in our study. Nevertheless, when the effect of PAR was removed by using partial correlation, VPD showed much stronger correlation with SIF in soil water stressed plot than that in unstressed one both at diurnal and seasonal scales. These results revealed that soil water deficit might promote the effect of atmospheric water deficit on SIF. This study has great significance for the application of SIF in drought monitoring and health assessments in terrestrial ecosystem.

Decoupling of impact factors reveals the response of German winter wheat yields to climatic changes

Yield development of agricultural crops over time is not merely the result of genetic and agronomic factors, but also the outcome of a complex interaction between climatic and site-specific soil conditions. However, the influence of past climatic changes on yield trends remains unclear, particularly under consideration of different soil conditions. In this study, we determine the effects of single agrometeorological factors on the evolution of German winter wheat yields between 1958 and 2015 from 298 published nitrogen (N)-fertilization experiments. For this purpose, we separate climatic from genetic and agronomic yield effects using linear mixed effect models and estimate the climatic influence based on a coefficient of determination for these models. We found earlier occurrence of wheat growth stages, and shortened development phases except for the phase of stem elongation. Agrometeorological factors are defined as climate covariates related to the growth of winter wheat. Our results indicate a general and strong effect of agroclimatic changes on yield development, in particular due to increasing mean temperatures and heat stress events during the grain-filling period. Except for heat stress days with more than 31°C, yields at sites with higher yield potential were less prone to adverse weather effects than at sites with lower yield potential. Our data furthermore reveal that a potential yield levelling, as found for many West-European countries, predominantly occurred at sites with relatively low yield potential and about one decade earlier (mid-1980s) compared to averaged yield data for the whole of Germany. Interestingly, effects related to high precipitation events were less relevant than temperature-related effects and became relevant particularly during the vegetative growth phase. Overall, this study emphasizes the sensitivity of yield productivity to past climatic conditions, under consideration of regional differences, and underlines the necessity of finding adaptation strategies for food production under ongoing and expected climate change.

Modelling of nitrification inhibitor and its effects on emissions of nitrous oxide (N2O) in the UK

Global food demand requires increased uses of fertilizers, leading to nitrous oxide (N₂O) and nitrate leaching due to overuse of fertilizers and poor timing between fertilizer application and plant growth. Using nitrification inhibitors (NIs) can reduce the N₂O emissions but the effectiveness of NIs strongly depend on environmental conditions, and their benefits have been limited due to less than optimal nitrogen rates, timing, quantity, and placement of NIs. Process-based modelling can be helpful in improving the understanding of nitrogen fertilizer with NIs and their effects in different environmental conditions and agricultural practices. But few studies of modelling NIs with application to agricultural soils have been performed. In this paper, we developed a sophisticated biogeochemical reaction process of NIs applied to agricultural soils, which account for the factions of NIs with fertilizer by combining the application rate, soil moisture, and temperature within the DeNitrification DeComposition (DNDC) framework. This model was tested against the data from two agricultural farms in Preston Wynne and Newark in the UK. The results agreed well with the measured data and captured the measured soil moistures and N₂O emissions. In Newark, the average Mean Absolute Error of all blocks is 8.78 and 5.45 for ammonium nitrate or urea respectively while in Preston Wynne, 3.48 and 3.14. The results also showed that the warming climate can greatly reduce the efficiency of nitrification inhibitors, which will further amplify the greenhouse gas impacts. The modified DNDC model of nitrification inhibitor modules can reliably simulate the inhibitory effect of NIs on N₂O emissions and evaluate the efficiency of NIs. This enables end-users to optimize the amount of NIs used according to the time and climate conditions of fertilizer application for increasing crop yield and reducing N₂O emissions and provides a useful tool for estimating the efficiency of NIs in agricultural management.

Differences in root surface adsorption, root uptake, subcellular distribution, and chemical forms of Cd between low- and high-Cd-accumulating wheat cultivars

The differences in the mechanism of cadmium (Cd) accumulation in the grains of different wheat (Triticum aestivum L.) cultivars remain unclear. Thus, we conducted a hydroponic experiment in a greenhouse to compare root surface adsorption, root uptake, subcellular distribution, and chemical forms of Cd between low- and high-Cd-accumulating wheat cultivars at seedling stage, to improve our understanding of the differences between cultivars. The results showed that Cd adsorbed on the root surface was mainly in a complexed form, and the total amount of Cd on the Yaomai16 (YM, high-Cd-accumulating genotypes) root surface was higher (p < 0.05) than that on Xinmai9817 (XM, low-Cd-accumulating genotypes). A large amount of Cd ions adsorbed on root surface would cause plant damage and inhibit growth. Comparing the root-to-shoot translocation factors of Cd, the transfer coefficients of YM were 1.017, 1.446, 1.464, and 1.030 times higher than those of XM under 5, 10, 50, and 100 μmol L^-1 Cd treatments, respectively. The subcellular distribution of Cd under Cd exposure is mainly in the cell wall and soluble fraction. The proportions of Cd in YM shoot soluble fraction were higher than those in XM, which was the main detoxification mechanism limiting the activity of Cd and may be responsible for low Cd accumulation in grains, while the effects of the chemical forms of Cd on migration and detoxification were not found to be related to Cd accumulation in the kernels.

Crop breeding has increased the productivity and leaf wax n-alkane concentration in a series of five winter wheat cultivars developed over the last 60 years

Plant wax n-alkanes are a major constituent of the leaf and grain surface. In this study, we explored what can be learned from the abundance and carbon isotopic composition (δ¹³C) of n-alkanes in historical winter wheat cultivars. We investigated leaf and grain wax n-alkane concentration (Σ_alkLand Σ_alkG) and carbon isotopes (δ¹³C_alkL and δ¹³C_alkG) on C₂₉ as well as bulk leaf and grain carbon isotopes (δ¹³C_bulkL and δ¹³C_bulkG) to assess if these wax components changed across five wheat cultivars released from the 1950s to the early 2010s. Results showed that Σ_alkL and grain yield increased, while δ¹³C_alkL and δ¹³C_bulkL decreased across the historical wheat cultivars. We found a significant correlation between Σ_alkL and shoot biomass at the early growth stage, and a strong correlation between Σ_alkL at the grain-filling stage and grain yield. Grain measures, including Σ_alkG, δ¹³C_alkG, and δ¹³C_bulkG did not correlate with crop production. Although δ¹³C_alkL and grain yield were not correlated at the flowering stage, they were correlated at the grain-filling stage under dry conditions. Our results indicate that increased Σ_alkL has been indirectly selected in breeding efforts to improve crop production in winter wheat, suggesting that greater leaf waxiness confers advantages for crop growth.

The influence of excess precipitation on winter wheat under climate change in China from 1961 to 2017

Winter wheat is one of China's most important staple food crops, and its growth and productivity are influenced by climate. Given its importance, we investigated the influence of excess precipitation under recent climate change on winter wheat in east-central China during 1961-2017. Although annual precipitation in the studied region decreased slightly, it increased during the winter wheat flowering and maturity period (May to June). Concurrently, the number of late growing season sunshine hours decreased. Our results showed that about 44% of the years with excess precipitation and less than normal radiation (16 years) were associated with decreasing winter wheat yields. Furthermore, during most years, precipitation of 50% above normal resulted in large decreases in winter wheat production in Jiangsu and Anhui provinces, some of the wetter parts of the studied region. These results indicated that the grain yield variability of winter wheat was mainly influenced by excess precipitation in May, where precipitation could explain 70%-78% of yield variability in the wet parts. Moreover, excess precipitation can induce Fusarium head blight as well as wheat sprouting of pre-harvest, both affecting the grain quality of winter wheat. Projected increases in precipitation throughout the 21st century in the studied region, warrants further studies of how to maintain the winter wheat production in a changing climate.

Evaluating the performance of SALTMED model under alternate irrigation using saline and fresh water strategies to winter wheat in the North China Plain

The effective water management in the North China Plain (NCP) needs a tool to predict winter wheat production due to water quality. A large quantity of brackish water is stored underground in this region, and whether this water can be used properly in agriculture is becoming a crucial issue that is about to be resolved. The SALTMED model is a generic modeling tool for efficient irrigation management strategies, especially for cyclic use of saline and fresh water as well as different water qualities, and it still needs further investigation for alternate irrigation using saline and fresh water at different growth stages of winter wheat. Therefore, the aim of this investigation was to evaluate the performance of SALTMED model and simulate the production of winter wheat grown under different irrigation strategies. Irrigation strategies comprised rain-fed cultivation (NI), fresh and saline water irrigation (FS), saline and fresh water irrigation (SF), saline water irrigation (SS), and fresh water irrigation (FF). Three-year observed data were used for the validations of SALTMED model. The values of evaluation indices of relative error, RMSE, NRMSE, index of agreement (D-index), and R² between simulated and observed grain yield were 6.8%, 0.8, 10.7, 0.9, and 0.9, respectively. The model results supported and matched the observed data and indicated similar differences among the irrigated and rain-fed treatments. It is concluded that the SALTMED model is able to predict grain yield of winter wheat and its productivity under the alternate irrigation using saline and fresh water and their interaction in the climate condition of the NCP.