Seed vectored bacterial endophyte Bacillus pumilus protect sorghum (Sorghum bicolor L.) seedlings from a fungal pathogen Rhizoctonia solani

• Published in: Biological control 2023-08, Vol.183, p.105249, Article 105249
• Main Authors: Kumar, Kanchan, Pal, Gaurav, Verma, Anand, Kumar, Deepak, Shukla, Pooja, Verma, Satish K.
• Format: Article
• Language: English
• Subjects: Bacillus pumilus; Biocontrol; Live-dead staining; Rhizoctonia solani; Seed endophytic bacteria; Seedling protection
• ISSN: 1049-9644
• DOI: 10.1016/j.biocontrol.2023.105249

•Bacterial seed endophytes of sorghum inhibited the growth of fungal pathogens.•The presence of surfactin (Sfp) gene was confirmed in Bacillus pumilus.•B. pumilus and its lipopeptide extract caused structural deformations in R. solani.•B. pumilus significantly protected the sorghum seedlings from R. solani infection.•B. pumilus up-regulated the expression of defense genes in sorghum seedlings. The goal of this study was to evaluate the role of seed endophytic bacteria (SEB) in fungal disease protection in sorghum seedlings. Total six SEB, including two Bacillus spp. (SM1 and SM6), and four Paenibacillus spp. (SM2, SM3, SM4, and SM5) were isolated from sorghum seeds. All isolates produced auxin while only SM3 isolate showed phosphate solubilization activity. All SEB inhibited the growth of tested fungal pathogens. Bacillus pumilus (SM1) and Bacillus subtilis (SM6) showed positive drop collapse assay, and presence of surfactin gene was also screened in their genomes. Further, lipopeptides extracted from SM1 and SM6 strongly inhibited Rhizoctonia solani growth in disc diffusion assay. Live-dead staining and fluorescence microscopy revealed the structural deformations and cell death in R. solani by lipopeptides. In microcosm assay, seeds inoculated with B. pumilus significantly protected the seedlings from Rhizoctonia infection. B. pumilus inoculated seedlings showed significant increase in the levels of PAL and SOD enzymes and their gene expressions (2.76, 2.00 and 4.61, 2.25 folds, respectively) compared to control. PR1 gene expression was also increased by 2.68 folds compared to the control. Present study concludes that sorghum seeds inhabit SEB like B. pumilus which is crucial in protecting seedlings from R. solani by producing lipopeptides, enhancing antioxidant and defense enzymes level and their gene expressions. This study is significant in terms of its originality which presents a first report on SEB of sorghum roles in seedlings protection against soil borne fungal pathogen like Rhizoctonia solani.