Improved photosynthetic characteristics correlated with enhanced biomass in a heterotic F1 hybrid of maize (Zea mays L.)

Disentangling the Heterosis in Biomass Production and Radiation Use Efficiency in Maize: A Phytomer-Based 3D Modelling Approach

Maize (Zea mays L.) benefits from heterosis in-yield formation and photosynthetic efficiency through optimizing canopy structure and improving leaf photosynthesis. However, the role of canopy structure and photosynthetic capacity in determining heterosis in biomass production and radiation use efficiency has not been separately clarified. We developed a quantitative framework based on a phytomer-based three-dimensional canopy photosynthesis model and simulated light capture and canopy photosynthetic production in scenarios with and without heterosis in either canopy structure or leaf photosynthetic capacity. The accumulated above-ground biomass of Jingnongke728 was 39% and 31% higher than its male parent, Jing2416, and female parent, JingMC01, while accumulated photosynthetically active radiation was 23% and 14% higher, correspondingly, leading to an increase of 13% and 17% in radiation use efficiency. The increasing post-silking radiation use efficiency was mainly attributed to leaf photosynthetic improvement, while the dominant contributing factor differs for male and female parents for heterosis in post-silking yield formation. This quantitative framework illustrates the potential to identify the key traits related to yield and radiation use efficiency and helps breeders to make selections for higher yield and photosynthetic efficiency.

Expression Patterns Divergence of Reciprocal F1 Hybrids Between Gossypium hirsutum and Gossypium barbadense Reveals Overdominance Mediating Interspecific Biomass Heterosis

Hybrid breeding has provided an impetus to the process and achievement of a higher yield and quality of crops. Interspecific hybridization is critical for resolving parental genetic diversity bottleneck problems. The reciprocal interspecific hybrids and their parents (Gossypium hirsutum and Gossypium barbadense) have been applied in this study to elucidate the transcription regulatory mechanism of early biomass heterosis. Phenotypically, the seed biomass, plant height over parent heterosis, leaf area over parent heterosis, and fresh and dry biomass were found to be significantly higher in hybrids than in parents. Analysis of leaf areas revealed that the one-leaf stage exhibits the most significant performance in initial vegetative growth vigor and larger leaves in hybrids, increasing the synthesis of photosynthesis compounds and enhancing photosynthesis compound synthesis. Comparative transcriptome analysis showed that transgressive down-regulation (TDR) is the main gene expression pattern in the hybrids (G. hirsutum × G. barbadense, HB), and it was found that the genes of photosystem I and Adenosine triphosphate (ATP)-binding may promote early growth vigor. Transgressive up-regulation (TUR) is the major primary gene expression pattern in the hybrids (G. barbadense × G. hirsutum, BH), and photosystem II-related genes mediated the performance of early biomass heterosis. The above results demonstrated that overdominance mediates biomass heterosis in interspecific hybrid cotton and the supervisory mechanism divergence of hybrids with different females. Photosynthesis and other metabolic process are jointly involved in controlling early biomass heterosis in interspecific hybrid cotton. The expression pattern data of transcriptome sequencing were supported using the qRT-PCR analysis. Our findings could be useful in theoretical and practical studies of early interspecific biomass heterosis, and the results provide potential resources for the theoretical and applied research on early interspecific biomass heterosis.

A model-guided holistic review of exploiting natural variation of photosynthesis traits in crop improvement

Breeding for improved leaf photosynthesis is considered as a viable approach to increase crop yield. Whether it should be improved in combination with other traits has not been assessed critically. Based on the quantitative crop model GECROS that interconnects various traits to crop productivity, we review natural variation in relevant traits, from biochemical aspects of leaf photosynthesis to morpho-physiological crop characteristics. While large phenotypic variations (sometimes >2-fold) for leaf photosynthesis and its underlying biochemical parameters were reported, few quantitative trait loci (QTL) were identified, accounting for a small percentage of phenotypic variation. More QTL were reported for sink size (that feeds back on photosynthesis) or morpho-physiological traits (that affect canopy productivity and duration), together explaining a much greater percentage of their phenotypic variation. Traits for both photosynthetic rate and sustaining it during grain filling were strongly related to nitrogen-related traits. Much of the molecular basis of known photosynthesis QTL thus resides in genes controlling photosynthesis indirectly. Simulation using GECROS demonstrated the overwhelming importance of electron transport parameters, compared with the maximum Rubisco activity that largely determines the commonly studied light-saturated photosynthetic rate. Exploiting photosynthetic natural variation might significantly improve crop yield if nitrogen uptake, sink capacity, and other morpho-physiological traits are co-selected synergistically.

Glomus mosseae and Pseudomonas fluorescens Application Sustains Yield and Promote Tolerance to Water Stress in Helianthus annuus L

The inoculation of sunflower (Helianthus annuus L.) plants with arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) can significantly enhance its growth and yield in a sustainable manner. Drought tolerance is mediated by a combination of direct AMF and PGPR benefits that boost the plant’s natural ability to cope with stress, whereas drought mitigation is mediated by indirect AMF and PGPR benefits and increased water uptake. An experiment was carried out to demonstrate the interactive effects of AMF (Glomus mosseae) alone or in association with PGPR (Pseudomonas fluorescens) under water-stressed conditions in order to assess their biofertilizer efficiency. Accordingly, various morphological and biochemical parameters were studied, and the results suggested that all the co-inoculation treatments displayed beneficial effects. Still, the combination of G. mosseae + P. fluorescens showed the maximum increment in all the parameters considered, i.e., plant height and weight, leaves length and width, number of leaves per plant, specific leaf weight, relative leaf water content (RLWC), photosynthetic efficiency, seed length, width, and area, seed yield per plant, number of seeds per flower, days to 50% flowering, days to maturity, flower and head diameter, harvest index, oil content, fatty acid composition (palmitic acid, oleic acid, stearic acid, and linoleic acid), and total yield. The improvement in different parameters may be attributed to the increased availability of nutrients due to the symbiotic association of AMF and PGPR with plant roots along with enhanced root structures for more water absorption under stressed conditions. Therefore, the results suggested that they offer a promising bio-control strategy for crop protection as biofertilizers combined in one formulation.

Improving photosynthesis to increase grain yield potential: an analysis of maize hybrids released in different years in China

In this work, we sought to understand how breeding has affected photosynthesis and to identify key photosynthetic indices that are important for increasing maize yield in the field. Our 2-year (2017-2018) field experiment used five high-yielding hybrid maize cultivars (generated in the 1970s, 2000s, and 2010s) and was conducted in the Xinjiang Autonomous Region of China. We investigated the effects of planting density on maize grain yield, photosynthetic parameters, respiration, and chlorophyll content, under three planting density regimens: 75,000, 105,000, and 135,000 plants ha^-1. Our results showed that increasing planting density to the medium level (105,000 plants ha^-1) significantly increased grain yield (Y) up to 20.32% compared to the low level (75,000 plants ha^-1). However, further increasing planting density to 135,000 plants ha^-1 did not lead to an additional increase in yield, with some cultivars actually exhibiting an opposite trend. Interestingly, no significant changes in photosynthetic rate, dark respiration, stomatal density, and aperture were observed upon increasing planting density. Moreover, our experiments revealed a positive correlation between grain yield and the net photosynthetic rate (P_n) upon the hybrid release year. Compared to other cultivars, the higher grain yield obtained in DH618 resulted from a higher 1000-kernel weight (TKW), which can be explained by a longer photosynthetic duration, a higher chlorophyll content, and a lower ratio of chlorophyll a/b. Moreover, we found that a higher leaf area per plant and the leaf area index (HI) do not necessarily result in an improvement in maize yield. Taken together, we demonstrated that higher photosynthetic capacity, longer photosynthetic duration, suitable LAI, and higher chlorophyll content with lower chlorophyll a/b ratio are important factors for obtaining high-yielding maize cultivars and can be used for the improvement of maize crop yield.

Improving photosynthesis to increase grain yield potential: an analysis of maize hybrids released in different years in China

In this work, we sought to understand how breeding has affected photosynthesis and to identify key photosynthetic indices that are important for increasing maize yield in the field. Our 2-year (2017-2018) field experiment used five high-yielding hybrid maize cultivars (generated in the 1970s, 2000s, and 2010s) and was conducted in the Xinjiang Autonomous Region of China. We investigated the effects of planting density on maize grain yield, photosynthetic parameters, respiration, and chlorophyll content, under three planting density regimens: 75,000, 105,000, and 135,000 plants ha^-1. Our results showed that increasing planting density to the medium level (105,000 plants ha^-1) significantly increased grain yield (Y) up to 20.32% compared to the low level (75,000 plants ha^-1). However, further increasing planting density to 135,000 plants ha^-1 did not lead to an additional increase in yield, with some cultivars actually exhibiting an opposite trend. Interestingly, no significant changes in photosynthetic rate, dark respiration, stomatal density, and aperture were observed upon increasing planting density. Moreover, our experiments revealed a positive correlation between grain yield and the net photosynthetic rate (P_n) upon the hybrid release year. Compared to other cultivars, the higher grain yield obtained in DH618 resulted from a higher 1000-kernel weight (TKW), which can be explained by a longer photosynthetic duration, a higher chlorophyll content, and a lower ratio of chlorophyll a/b. Moreover, we found that a higher leaf area per plant and the leaf area index (HI) do not necessarily result in an improvement in maize yield. Taken together, we demonstrated that higher photosynthetic capacity, longer photosynthetic duration, suitable LAI, and higher chlorophyll content with lower chlorophyll a/b ratio are important factors for obtaining high-yielding maize cultivars and can be used for the improvement of maize crop yield.

The influence of vermicomposting on photosynthetic activity and productivity of maize (Zea mays L.) crop under semi-arid climate

Food production and waste recycling are the two major issues faced globally with rapidly increasing population. Recycling organic wastes to crop amendments could be a possible solution to these issues. Earthworms transfer organic waste to compost, which is used to grow crops and increase crop productivity. This study assessed the impact of vermicompost produced from the residues of six desert plant species, i.e., (Ziziphus mauritiana, Aerva javanica, Calligonum comosum, Sacchrum benghalens, Calligonum polygonoides and Prosopis cineraria) combined with farmyard manure (5 t ha-1) on growth, yield and photosynthetic activity of maize crop. Earthworm species Eisenia fetida (Savigny, 1826) was used to prepare vermicomposting of all tested plant species. The desert species were collected from natural habitats, chopped, dried, mixed with FYM and then earthworms were released to prepare the vermicompost. The earthworms were excluded twenty days after release and resultant was considered as compost and used in the experiment. Results revealed that application of P. cineraria vermicompost resulted in the highest plant height (75.33 cm), stem diameter (22.66 mm), cob length (17.66 cm), number of grains/cob (374.67), 1000-grain weight (260.41 g) and grains yield (3.20 t/ha). Application of P. cineraria vermicompost resulted in the highest uptake of macronutrients, i.e., N (91.01%), P (22.07%), K (80.41%), micronutrients, i.e., Fe (19.07 ppm), Zn (40.05 ppm), and phenolic contents (150). Application of P. cineraria vermicompost also resulted in the highest quantum photosynthetic yield (0.42 mole C/mole of photon), chlorophyll florescence (355.18 moles of photon m-2s-1) and electron transport rate (310.18 micro mole m-2s-1). It is concluded that vermicomposting has the potential to improve growth and yield of maize crop. Particularly, application of vermicompost obtained from P. cineraria can be used to improve the growth and yield of maize crop. Nonetheless, field trials are necessary for a wide scale recommendation.