Antagonistic Potential of Novel Endophytic Bacillus Strains and Mediation of Plant Defense against Verticillium Wilt in Upland Cotton

Abstract

Verticillium wilt caused by Verticillium dahliae is a threatening disease of cotton, causing economic loss worldwide. In this study, nine endophytic Bacillus strains isolated from cotton roots exhibited inhibitory activity against V. dahliae strain VD-080 in a dual culture assay. B. altitudinis HNH7 and B. velezensis HNH9 were chosen for further experiments based on their high antagonistic activity. The secondary metabolites of HNH7 and HNH9 also inhibited the growth of VD-080. Genetic marker-assisted detection revealed the presence of bacillibactin, surfactin, bacillomycin and fengycin encoding genes in the genome of HNH7 and HNH9 and their corresponding gene products were validated through LC-MS. Scanning electron microscopy revealed mycelial disintegration, curling and shrinkage of VD-080 hyphae after treatment with methanolic extracts of the isolated endophytes. Furthermore, a significant reduction in verticillium wilt severity was noticed in cotton plants treated with HNH7 and HNH9 as compared to control treatments. Moreover, the expression of defense-linked genes, viz., MPK3, GST, SOD, PAL, PPO and HMGR, was considerably higher in plants treated with endophytic Bacillus strains and inoculated with VD-080 as compared to control.

Bacillus circulans GN03 Alters the Microbiota, Promotes Cotton Seedling Growth and Disease Resistance, and Increases the Expression of Phytohormone Synthesis and Disease Resistance-Related Genes

“…To infect cotton roots favorably, V. dahliae can selectively steer the local microbiome by its effector proteins, and increasing reports have shown that the microbiome inside and outside a plant plays an crucial role in its health (Snelders et al, 2020). Bacillus species can produce some antibiotics, which can directly strangle the growth of the pathogen or induce systemic resistance in plants (Hasan et al, 2020). In our study, it was found that GN03 possess antibiotics (streptomycin, surfactin, The tree was built using a single copy homologous gene using the neighbor joining method with a bootstrap value of 1,000.…”

“…Some chemicals, such as benomyl and acibenzolar-S-methyl, seem to work for Verticillium wilt, but they are not environment friendly (Goicoechea, 2009). Therefore, application of PGPB to control this disease is a safer and better alternative to protect upland cotton from Verticillium wilt (Hasan et al, 2020). Accordingly, beneficial PGPB with inhibitory action against V. dahliae are a promising biocontrol agent for the control of cotton Verticillium wilt.…”

“…Accordingly, beneficial PGPB with inhibitory action against V. dahliae are a promising biocontrol agent for the control of cotton Verticillium wilt. To date, some researchers have isolated multiple strains with biocontrol activities against V. dahliae from Bacillus, Enterobacter, Paenibacillus, Pseudomonas, Serratia, and Streptomyces genera (Erdogan and Benlioglu, 2010;Zhang et al, 2018;Cheng et al, 2020;Hasan et al, 2020;Sherzad and Canming, 2020;Tao et al, 2020;Zhang et al, 2020).…”

Biological Control of Plant Pathogens: A Global Perspective

“…These beneficial associations boost plant health and crop productivity by increasing nutrient availability, releasing plant growth-stimulating hormones, decreasing pathogen/pest-caused diseases, or improving the environmental stress resistance [ 39 ]. Antibiotics, endotoxins, bacteriocins, siderophores, hydrolytic enzymes, hydrogen cyanide (HCN), phenazine-1-carboxylic acid (PCA), 2,4-diacetylphloroglucinol (DAPG), and other secondary metabolites produced by certain rhizosphere bacteria kill pathogens, thus preventing disease development [ 39 , 43 , 44 , 47 , 49 , 50 , 51 , 52 , 53 , 54 ]. Some PGPRs utilized in the control of plant pests and diseases are discussed below.…”

“…Furthermore, when compared to control treatments, cotton plants treated with two Bacillus strains (HNH7 and HNH9) showed a considerable reduction in verticillium wilt severity. Moreover, the expression of some defense-related genes was significantly higher in plants treated with Bacillus strains and inoculated with VD-080 [ 54 ].…”