Suppression of Bipolaris Leaf Blotch and Improvement of Wheat Growth by Plant Growth Promoting Rhizobacteria Bacilli

Abstract

Bipolaris leaf blotch, induced by Bipolaris sorokiniana, poses a notable risk to wheat cultivation, resulting in considerable annual declines in yield. Plant Growth-Promoting Rhizobacteria (PGPR) are acknowledged for their colonization of the wheat rhizosphere and provision of various advantages to plants, including disease control and improved growth. This investigation seeks to explore the feasibility of utilizing PGPR strains as a viable substitute for harmful chemical inputs to combat Bipolaris leaf blotch and foster the growth of three wheat varieties while pinpointing the optimal PGPR-wheat variety combination for future field application. Laboratory and pot experiments were conducted utilizing a Completely Randomized Design (CRD) with three replications for each treatment. Data Analysis Involved Analysis of Variance (ANOVA) followed by Duncan's Multiple Range Test (DMRT) to ascertain the statistical significance (p = 0.05) of treatment effects. Following an initial screening of seven PGPR isolates for their in vitro antifungal activities against B. sorokiniana, two promising antagonists, Bacillus subtilis PPB9 and Bacillus amyloliquefaciens PPB12, were selected for further evaluation due to their multiple plant-growth-promoting and biocontrol characteristics. Subsequent pot experiments in a growth room revealed that seed treatment followed by foliar spraying with these strains effectively suppressed Bipolaris leaf blotch infection across all three wheat varieties-Kanchan, Shatabdi and BARI gom-27, compared to the untreated control. Additionally, PGPR treatment led to significantly (p = 0.05) higher levels of root and shoot growth compared to untreated plants. The efficacy of the two PGPR strains varied in disease suppression and growth promotion, with B. amyloliquefaciens PPB12 outperforming B. subtilis PPB9. Similarly, among the three wheat varieties, Shatabdi exhibited a more prominent response to PGPR treatment. These findings emphasize the importance of carefully selecting rhizobacterial strains to effectively manage Bipolaris leaf blotch and enhance wheat growth. The study accentuates the significant potential of Bacillus strains and their compatibility with a preferred wheat variety, offering a novel and sustainable alternative for Bipolaris leaf blotch management and wheat cultivation improvement.