Endophytic bacteria Bacillus velezensis NKG50 as a potential biocontrol agent of Ascochyta blight on chickpea

Abstract

One of chickpea crops most devastating and economically relevant fungal diseases is Ascochyta rabiei, the causal agent of Ascochyta blight. The traditional agricultural management of the disease requires a complex combination of cultural, chemical, and genetic strategies. To develop a more effective management strategy, with low economic and environmental costs, we isolated 43 endophytic bacteria from asymptomatic chickpea plants native to our soils region. We tested their antifungal effect with mycelial growth and conidia germination inhibition tests. Our best candidate was NKG50 isolate, which inhibited A. rabiei growth by more than 85% in the dual test, more than 65% by cell-free supernatants, and inhibited conidia germination by 90%. This antagonistic ability was confirmed in leaflet and greenhouse assays, with a significant reduction in disease severity in both scales. The isolated NKG50 genome was completely sequenced and identified as Bacillus velezensis NKG50. We found 13 gene clusters associated with secondary metabolites, and five of them with an unknown function and or nature previously reported for B. velezensis. This study demonstrated for the first time that B. velezensis NKG50 is a strong candidate for the biocontrol of Ascochyta blight in Argentina.