Background: Verticillium dahliae, the causal agent of Verticillium wilt, is notoriously invasive in many crops and has been involved in numerous epidemics worldwide. Bacillus species, as representatives of biocontrol bacteria, produce a variety of lipopeptides (LPs), which are useful as biofungicides to many pathogenic fungi, including Verticillium dahliae. This study will explore the mechanism of resistance of V. dahliae to Bacillus and biocontrol bacteria.Results: By using in vitro confrontation bioassays, we found that under the stress induced by Bacillus, the spore vitality of V. dahliae with larger colonies was higher, and more abundant microsclerotia were formed. Then, according to the RNA-Seq analysis, the target of rapamycin (TOR) and mitophagy pathways were enriched among the significantly upregulated 542 genes observed in two co-culture groups with different colony sizes. In addition, in the group of V. dahliae with large colonies, the pathways related to cell wall synthesis, microsclerotia formation and the clearance of reactive oxygen species were regulated, and the expression of genes was up-regulated.Conclusion: This study found that the larger colonies of V. dahliae were more resistant to the antagonistic actions of Bacillus and the likelihood of the formation of homeostasis. Therefore, the prevention of Verticillium wilt by Bacillus is more effective than the treatment of an active fungal infection. These transcriptomic insights provide direction for the use of fungicides in the prevention and treatment of diseases such as Verticillium wilt.

Purpose In agricultural practices, continuous cultivation of genetically modified crops with high commercial value has a definite impact on soil microbial diversity. Soil microorganisms directly define the operational degree and function realization of the soil ecosystem. To understand the safety of environmental release, we studied the effects of continuous cropping of transgenic cotton on the diversity of bacterial communities in the rhizosphere soil. Methods We have applied a high-throughput sequencing method and compared the bacterial community structure as well as diversity of rhizosphere soil of the transgenic cotton line (25C-1) and its parent cotton line (TH2). Result Structural analysis of the bacterial community showed that Arthrobacter and Sphingomonas are significantly enriched after continuous cropping of transgenic cotton lines and had a positive impact on the soil’s ecological environment. Interestingly, parameters of the physical and chemical properties of soil used for the continuous cropping of the two cotton lines for 3 consecutive years show no detectable change, other than total nitrogen. Notably, Spearman’s correlation analysis suggests that total nitrogen is the key environmental factor that affects the bacterial community of the soil used to cultivate the transgenic cotton. Conclusion We did not find a notable difference in species diversity between the two samples. However, the proportions of beneficial bacteria (Arthrobacter and Sphingomonas) increased and the total nitrogen content has changed in 3 years. These results provide necessary insights into the function and role of bacteria in transgenic cotton. This study will help future investigators assess the potential ecological risks of genetically modified plants.

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Verticillium dahliae causes disease symptoms in its host plants; however, due to its rapid variability, V. dahliae is difficult to control. To analyze the reason for this pathogenic differentiation, 22 V. dahliae strains with different virulence were isolated from a cotton farm. The genetic diversity of cotton varieties make cotton cultivars have different Verticillium wilt resistance, so the Xinluzao 7 (susceptible to V. dahliae), Zhongmian 35 (tolerant), and Xinluzao 33 (resistant) were used to investigate the pathogenicity of the strains in a green house. Vegetative compatibility groups (VCGs) assays, Internal Transcribed Spacer (ITS) PCR, and pathogenicity analysis showed that SHZ-4, SHZ-5, and SHZ-9 had close kinship and significantly different pathogenicity. Transcriptome sequencing of the three strains identified 19 of 146 unigenes in SHZ-4_vs_ SHZ-5, SHZ-5_vs_ SHZ-9, and SHZ-4_vs_ SHZ-9. In these unigenes, three proteinase and four polysaccharide degrading hydrolases were found to be associated with the pathogenicity. However, due to a number of differentially expressed genes in the transport, these unigenes not only played a role in nutrition absorption but might also contribute to the resistance of sugar-induced hyperosmosis. Moreover, the tolerance ability was positively related to the pathogenicity of V. dahliae. This resistance to sugar-induced hyperosmosis might help V. dahliae to access the nutrition of the host. The pathogenicity of V. dahliae correlated with the resistance of sugar-induced-hyperosmosis, which provides clues for the cultivation of V. dahliae resistant varieties.