Selected rhizobacteria strains as potential growth promoters and biocontrol agents against chocolate spot disease in faba bean grown in pots

Abstract

The faba bean is a grain legume used for food and feed. It suffers from several yield limiting diseases. Botrytis fabae Sard is a fungal pathogen which causes chocolate spot disease in faba bean all over the world. Searching for solutions to the problem of yield loss due to B. fabae is critical. One sustainable solution is the utilization of plant-growth-promoting rhizobacteria as biocontrol agents. This study aimed to demonstrate the effect of rhizobacteria strains on controlling chocolate spots and promoting the growth of faba beans under pot conditions. Three rhizobacteria strains that previously demonstrated promising potential were used and tested for antagonistic activity against B.fabae in dual culture. All tested rhizobacterial strains inhibited the mycelial growth of B.fabae with different potential, and Chryseobacterium strain GY04 showed a maximum percent of mycelial growth inhibition of 72.38%. Also, all rhizobacteria strains significantly reduced the incidence and severity of chocolate spot disease, with different efficacy in both faba bean varieties under pot conditions. Chryseobacterium strain GY04 showed the highest disease severity reduction on the local variety at 75 (79.62%) and 90 (73.57%) days after sowing. Rhizobacterium Pseudomonas chlororaphis GY07 resulted in the highest disease severity reduction on the Dosha variety (80.12, 43.85%) at 75 and 90 days after sowing, respectively. All tested rhizobacteria improved the main plant growth parameters in both varieties. The rhizobacterial strains examined in this study could be used as biocontrol against Chocolate spot disease and as growth promoters under pot conditions.