Assessment of fungal and bacterial bioagents against Bipolaris sorokiniana inciting spot blotch on barley (Hordeum vulgare)

In India, spot blotch disease caused by Bipolaris sorokiniana is one of the major constraints in barley (Hordeum vulgare L.) production. The present study was carried out during 2022–23 at ICAR-Indian Agriculture Research Institute, New Delhi to identify promising biocontrol agents, which can act as eco-friendly alternatives to chemicals against Bipolaris sorokiniana inciting spot blotch on barley (Hordeum vulgare L.). In this study, 18 isolates of Trichoderma asperellum, 15 isolates of Trichoderma harzianum and 5 bacterial species were tested against B. sorokiniana under in vitro and in planta conditions. In the dual culture assays, Trichoderma asperellum 8686 and Trichoderma asperellum 8687 showed significantly highest per cent disease inhibition of 71.73% and 71.37% respectively. Among bacterial strains, Pseudomonas fluorescens and Bacillus amyloliquefaciens showed significantly good per cent disease inhibition of 64.09% and 57.09% respectively. B. subtilis and Pantoea spp. did not show any pathogen inhibition. In addition, the superior bioagents were also screened out. In the studies on in planta assays, Bacillus amyloliquefaciens (per cent disease control-55.19%) was found most effective for seed treatment against B. sorokiniana. Post-inoculation with biocontrol agents revealed that Bacillus amyloliquefaciens was at par with Trichoderma asperellum and Pseudomonas fluorescens against B. sorokiniana. Additionally, a combination of seed treatment, pre and post-inoculation treatment of biocontrol agents revealed that Bacillus amyloliquefaciens and Trichoderma asperellum 8686 were at par with Trichoderma harzianum (Pusa Th3) against B. sorokiniana. Overall, Bacillus amyloliquefaciens was more effective and consistent to manage spot blotch disease.