The effects and interrelationships of intercropping on Cotton Verticillium wilt and soil microbial communities

Effects of saffron-grape intercropping on saffron flower number and rhizosphere microbial community

BACKGROUND

Saffron (Crocus sativus L.) is a valuable herb. With the increasing demand for saffron, people are starting to focus on how to increase its yields. Intercropping and microbial interactions have a positive effect on plant yield, including enhanced soil fertility, enriched microbial diversity, reduced pest and disease incidences, and improved plant growth. However, the impact of intercropping saffron with other plants on saffron yields and soil microbial community diversity remains unclear. In our study, we counted the number of saffron flowers in two cropping patterns (saffron monoculture and saffron-grape intercropping), and analyzed the microbial community diversity and composition using Illumina high-throughput sequencing methods based on 16 S and ITS amplicons.

RESULTS

The results showed that saffron-grape intercropping significantly increased number of flowers compared to saffron monoculture (P < 0.01). Saffron-grape intercropping influenced rhizosphere soil chemical properties and altered rhizosphere microbial communities. The pH of intercropped rhizosphere soil increased significantly from 5.84 to 6.43. Spearman's correlation revealed a significantly positive correlation between pH and Bacillus, Sphingomonas, Sphingobacterium, Halomonas, Pseudolabrys, and Dongia. Conversely, it showed a significant negative correlation with Pedobacter, Achromobacter, Tumebacillus, and Sphingopyxis in bacteria. In fungi, a significant negative correlation was observed. Although there was no significant difference in diversity, intercropping increased the observed richness and biodiversity of both bacteria and fungi compared to monoculture. The intercropping led to a higher relative abundance of bacterial genera such as Sphingomonas and Streptomyces, as well as fungal genera including Acremonium, Llyonectria, Penicillium, Cadophora, Plectosphaerella, and Tetracladium. Intercropping decreased the dominance of certain microbial taxa, including Fictibacillus, Microbacterium, and Glutamicibacter among bacterial genera, as well as Fusarium and Arthrographis among fungal genera. Additionally, functional analysis revealed that intercropping was significantly higher (P < 0.01) than monoculture in dark hydrogen oxidation, denitrification, nitrate denitrification, nitrous oxide denitrification, nitrite denitrification, and manganese oxidation. Plant pathogens decreased from 6.13% in monoculture to 2.46% in intercropping.

CONCLUSION

This study found that saffron-grape intercropping positively affected saffron yield. Based on the existing data, intercropping resulted in an increase in microbial communities, including some taxa previously identified as beneficial for other plants. These findings establish the foundation for the widespread application of saffron-grape intercropping and offer a promising strategy for increasing saffron yield.

The effect of Torreya grandis inter-cropping with Polygonatum sibiricum on soil microbial community

Background

Inter-cropping is a reasonable planting pattern between different plants. Inter-cropping of Torreya grandis with Polygonatum sibiricum is a relatively mature planting pattern in China, which has been applied to improve soil ecological environment and reduce the occurrence of pests and diseases in China. However, there is currently limited knowledge on the response of soil microbial communities to this practice.

Methods

In this study, we employed Illumina MiSeq sequencing coupled with Functional Annotation of Prokaryotic Taxa (FAPROTAX) and Fungi Functional Guild (FUNGuild) analyses to investigate the dynamic changes in soil microbial communities across seven treated groups [the bulk soil of the T. grandis inter-cropping with P. sibiricum (IB), the bulk soil for mono-cropping of P. sibiricum (PB), the bulk soil for mono-cropping of T. grandis (TB), the P. grandis rhizosphere soil of the T. grandis inter-cropping with P. sibiricum (IPR), the rhizosphere soil for mono-cropping of P. sibiricum (PR), the T. grandis rhizosphere soil of the T. grandis inter-cropping with P. sibiricum (ITR), and the rhizosphere soil for mono-cropping of T. grandis (TR)].

Results

The results showed that the rhizosphere soil of Torreya-Polygonatum inter-cropping exhibited higher microbial community richness, diversity and evenness than mono-cropping (ITR > TR, IPR > PR). Inter-cropping increased the abundance of Micrococcaceae, Xanthobacteraceae, Saitozyma, while decreased Bacillus, Burkholderia, Streptomyces, Cladosporium, and Gibberella significantly of the rhizosphere soil of T. grandis. Further, the abundance of pathogens, such as Fusarium and Neocosmospora, was higher in mono-cropping samples compared to inter-cropping. There existed distinct variations in bacterial and fungal communities among all groups except for IB and TB. The FAPROTAX and FUNGuild analyses results indicated that inter-cropping significantly enhanced soil microbial function associated with nutrient cycling and exhibited a consistent increase in the relative abundance of nitrogen-cycling and carbon-cycling bacteria, and decreased the abundance of plant pathogen guild in the inter-cropping sample ITR compared to the mono-cropping TR.

Conclusion

Our findings suggest that T. grandis inter-cropping with P. sibiricum not only enhance the diversity of soil microbial communities, but also improve the nitrogen and carbon cycling functions. In addition, the inter-cropping can effectively reduce the relative abundance of some soil-borne pathogens for T. grandis and P. sibiricum, indicating that this intercropping method may alleviate the impact of pathogens on crops, thus providing assistance for plant disease prevention and sustainable management.

Coal mining activities driving the changes in bacterial community

The mechanism of the difference in bacterial community composition caused by environmental factors in the underground coal mine is unclear. In order to reveal the influence of coal mining activities on the characteristics of bacterial community structure in coal seam, 16S rRNA gene amplicon sequencing technology was used to determine the species abundance, biodiversity, and gene abundance of bacterial community in a coal mine in Shanxi Province, and the environmental factors such as metal elements, non-metal elements, pH value, and gas concentration of coal samples were determined. The results showed that environmental factors and bacterial communities had obvious regional characteristics. Mining activities greatly affected the α diversity of bacterial communities, mining working face > main airway > roadway roof > unexposed coal seam > tunneling roadway. The bacterial community composition of each sample point is also very different. The main airway, roadway roof, and unexposed coal seam are dominated by Actinobacteria while the mining working face and tunneling roadway are dominated by Proteobacteria. Among the gene abundances of metabolic pathways in each site, Citrate cycle had the greatest difference, followed by glycine, serine and threonine metabolism, and oxidative phosphorylation and methane metabolism had little difference. RDA analysis showed that the environmental factors affecting the bacterial community were mainly cadmium, oxygen, hydrogen, and gas content. CCA analysis divided the bacterial community into three categories. Degradation functional bacteria are located in mining working face, bacteria that tolerate poor environments are located in main airway and tunneling roadway, and human pathogens are mostly located in roadway roof and unexposed coal seam. The research results would provide support for realizing green and safe mining in coal mines.

Complete genome sequence data of Pseudomonas nitroreducens L4, an endophyte isolated from cotton plants

Pseudomonas nitroreducens L4 was isolated from the interior of cotton plants, which showed strong biocontrol activity against Verticillium dahlia and other fungal pathogens. To elucidate the biocontrol mechanism, the genome sequence of L4 was sequenced using the Illumina and Nanopore sequencing platform. The assembled genome of L4 consisted of a single circular chromosome was 6,229,472 bp, with an average GC content of 64.95 %, 5,629 protein-coding genes, 72 tRNA, 16 rRNA and 1 tm RNA. Six secondary metabolite biosynthetic gene clusters are identified in the genome. The genome sequence provided a theoretical basis for analyzing the biocontrol mechanism of this strain.

Managing faba bean wilt disease through intercropping with wheat and reasonable nitrogen application: enhancing nutrient absorption and biochemical resistance in faba beans

Faba bean wilt disease is a key factor limiting its production. Intercropping of faba bean with wheat has been adopted as a prevalent strategy to mitigate this disease. Nitrogen fertilizer improves faba bean yield, yet wilt disease imposes limitations. However, faba bean-wheat intercropping is effective in controlling wilt disease. To investigate the effect of intercropping under varying nitrogen levels on the incidence of faba bean wilt disease, nutrient uptake, and biochemical resistance in faba bean. Field and pot experiments were conducted in two cropping systems: faba bean monocropping (M) and faba bean-wheat intercropping (I). At four nitrogen levels, we assessed the incidence rate of wilt disease, quantified nutrient uptake, and evaluated biochemical resistance indices of plants. The application of N decreased the incidence rate of wilt disease, with the lowest reduction observed in intercropping at the N2 level. N application at levels N1, N2, and N3 enhanced the content of N, P, K, Fe, and Mn as well as superoxide dismutase (SOD), phenylalanine ammonia lyase (PAL), and polyphenol oxidase (PPO) activities and defense gene expression in monocultured plants. Additionally, these levels increased the contents of total phenols, flavonoids, soluble sugars, and soluble proteins, and all reached their maximum in intercropping at the N2 level. The application of intercropping and N effectively controlled the occurrence of faba bean wilt disease by promoting nutrient absorption, alleviating peroxidation stress, and enhancing resistance in plants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01466-1.

Enhancing cotton sustainability: Multi-factorial intercropping, irrigation, and weed effects on productivity, quality and physiology

Drought stress and weed infestation are significant factors that significantly decrease cotton yield. Increasing the variety of plants within a cotton field ecosystem can strengthen its stability and protect it from susceptibility to both biotic and abiotic pressures. In this two-year experiment (2021 and 2022), the effects of intercropping systems (four growth conditions including mono- and inter-cropped cotton varieties Golestan and Hekmat with Nepeta crispa and dragon's head (Lallemantia iberica)), irrigation (three intervals of 3, 6, and 9 days), and weed competition (weed-free and weedy plots) on the agronomic performance, physiological characteristics, and seed quality of cotton in a semi-arid region of Iran were studied. In 2021, the volume of irrigation water applied was 9873, 6100, and 4650 m3 ha-1 for irrigation intervals of 3, 6, and 9 days, respectively. In 2022, the volumes were 9071, 5605, and 4272 m3 ha-1 for the corresponding irrigation intervals. Over two years, Xanthium strumarium, Amaranthus retroflexus, and Portulaca oleracea were the dominant weed species. Weeds had the most significant impact on total dry weight; weed control increased plant vigor and growth, ranging from 1.4 to 2.3 times, while weed impact on cottonseed yield ranged from 18% to 96% reduction. Increasing irrigation intervals resulted in reductions in various parameters, with decreases of 39%-80% in total dry weight, 34%-57% in cottonseed yield, and 48%-72% in lint yield. The harvest indices for seed cotton, cottonseed, and lint ranged from 35.3% to 56.5%, 18.3%-35.0%, and 15.4%-20.5%, respectively. Weeds were responsible for a 17% decrease in the 1000-seed weight. As the irrigation intervals increased from 3 days to 6 days and 9 days, the number of bolls per plant decreased by 19%-85%. Extending the irrigation interval from 3 days to 6 days and 9 days resulted in a substantial decrease in the photosynthetic rate, ranging from 42% to 92%. Mono-cropped Golestan performed well under unstressed conditions such as 3-day interval irrigation and weed-free conditions. On the other hand, intercropped Hekmat demonstrated better resilience to both moisture and weed stresses. The LER (Land equivalent ratio) indices of both intercropping systems were generally favorable, indicating higher productivity compared to sole cropping. The intercropping systems consistently showed the highest LER indices under weedy conditions, highlighting the significance of intercropping as a valuable method in integrated weed management.

Effects of Fe-modified digestate hydrochar at different hydrothermal temperatures on anaerobic digestion of swine manure

Hydrothermal carbonization temperature is a key factor in controlling the physico-chemical properties of hydrochar and affecting its function. In this study, effects of hydrochar and Fe-modified hydrochar (Fe-HC) prepared at 180 °C (180C-Fe), 220 °C (220C-Fe) and 260 °C (260C-Fe) on anaerobic digestion (AD) performance of swine manure was investigated. Among the three Fe-HCs, 220C-Fe had the highest amount of Fe and Fe2+ on the surface. The relative methane production of control reached 174 %-189 % in the 180C-Fe and 220C-Fe treatments between days 11 and 12. The degradation efficiency of swine manure was highest in the 220C-Fe treatment (61.3 %), which was 14.8 % higher than in the control. Fe-HC could act as an electron shuttle, stimulate the coenzyme F420 formation, increase the relative abundance of Methanosarcina and promote electron transport for acetotrophic methanogenesis in the AD. These findings are helpful for designing an efficient process for treating swine manure and utilizing digestate.

Investigating Verticillium wilt occurrence in cotton and its risk management by the direct return of cotton plants infected with Verticillium dahliae to the field

Verticillium wilt is one of the most crucial diseases caused by Verticillium dahliae that threatens the cotton industry. Statistical results showed that the return of cotton plants infected with V. dahliae to the field might be an essential cause of the continuous aggravation of cotton Verticillium wilt. The correlation among the cotton plants infected with V. dahliae returning to the field, the occurrence of Verticillium wilt, and the number of microsclerotia in rhizosphere soil need further investigation. A potted experiment was carried out to explore the effects of the direct return of cotton plants infected with Verticillium dahliae to the field on the subsequent growth and Verticillium wilt occurrence in cotton. As a risk response plan, we investigated the feasibility of returning dung-sand (i.e., insect excreta) to the field, the dung-sand was from the larvae of Protaetia brevitarsis (Coleoptera: Cetoniidea) that were fed with the V. dahliae-infected cotton plants. The results demonstrated that the return of the entire cotton plants to the field presented a promotional effect on the growth and development of cotton, whereas the return of a single root stubble or cotton stalks had an inhibitive effect. The return of cotton stalks and root stubble infected with V. dahliae increased the risk and degree of Verticillium wilt occurrence. The disease index of Verticillium wilt occurrence in cotton was positively correlated with the number of microsclerotia in the rhizosphere soil. The disease index increased by 20.00%, and the number of soil microsclerotia increased by 8.37 fold in the treatment of returning root stubble infected with V. dahliae to the field. No Verticillium wilt microsclerotia were detected in the feed prepared from cotton stalks and root stubble fermented for more than 5 days or in the transformed dung-sand. There was no risk of inoculation with Verticillium wilt microsclerotia when the dung-sand was returned to the field. The indirect return of cotton plants infected with V. dahliae to the field by microorganism-insect systems is worthy of further exploration plan of the green prevention and control for Verticillium wilt and the sustainable development of the cotton industry.