Endophytic Bacterium Bacillus velezensis NKG50 as a Potential Biocontrol Agent of Ascochyta Blight on Chickpea in Argentina

Abstract

One of the chickpea crop's most devastating and economically relevant fungal diseases is Ascochyta blight, caused by Ascochytarabiei. The traditional agricultural management of the disease requires a complex combination of cultural, chemical and geneticstrategies. To develop a more effective management strategy, with low economic and environmental costs, we isolated 43 en-dophytic bacteria from asymptomatic chickpea (Cicer arietinum) plants native to our soil's region in Argentina. We tested theirantifungal effect with mycelial growth and conidial germination inhibition tests. Our best candidate was the NKG50 isolate,which inhibited A. rabiei growth by more than 85% in the dual culture test of the bacterium versus the fungus, more than 65% bycell-free supernatants, and inhibited conidial germination by 90%. This antagonistic ability was confirmed in leaflet and wholeplant assays, with a significant reduction in disease severity in both kinds of assays. The isolated NKG50 genome was completelysequenced and identified as Bacillus velezensis NKG50. We found 13 gene clusters associated with secondary metabolites, andfive of them with an unknown function or nature previously reported for B. velezensis. This study demonstrated for the first timethe potential of B. velezensis NKG50 as a biocontrol agent for Ascochyta blight in Argentina.