Antagonistic potential of bacterial isolates from the rhizosphere of corn and avocado of the Naya-rit state against phytopathogen fungi of agricultural importance

Abstract

Six bacterial isolates recovered from the rhizosphere ofmaize and avocado in Nayarit, Mexico, were evaluated forantagonistic activity against soilborne vascular pathogens,including Fusarium oxysporum, F. stilboides, and Verticilliumsp. Partial 16S rRNA gene sequencing (99–100 % identity)identified the isolates as B acillus amyloliquefaciens ZJ-1, B.amyloliquefaciens ZJ-3, B. subtilis ZJ-19, Serratia marcescensZJ-157, Enterobacter cancerogenus ZJ-167, and E. bugandensisZJ-168. Cell-free supernatants of bacterial culturessignificantly reduced radial growth of Verticillium sp. (p ≤0.05), with inhibition exceeding 40 % in the Bacillus isolatesand E. cancerogenus ZJ-167, and approximately 20 % in S.marcescens ZJ-157 and E. bugandensis. Moderate inhibitionof F. stilboides was observed only for E. bugandensis ZJ-168(17.08 ± 1.54 %). No significant reduction in radial growthwas detected for F. oxysporum; however, distinct morphologicalalterations of the mycelium were observed. Protease activitywas associated with Bacillus isolates exhibiting strongerinhibition of Verticillium sp. All strains produced siderophoresand volatile organic compounds that reduced fungal growth.These findings indicate that fungal inhibition is associatedwith multiple complementary antagonistic mechanisms.