Biological control of Fusarium wilt caused by Fusarium equiseti in Vicia faba with broad spectrum antifungal plant-associated Bacillus spp.

Fusarium wilt caused by root infections by Fusarium equiseti is a serious disease of Vicia faba that causes significant economic losses in bean. Among management strategies, biological control is a sustainable alternative to chemical control, and Bacillus species emerge as suitable candidates. Bacillus strains have been developed in recent years as biocontrol agents of several plant diseases, mainly for fungal root disease control. In this study, 24 strains of Bacillus spp. were selected among 455 isolates obtained from V. faba plants for their antifungal activity against a broad-spectrum of phytopathogenic fungi belonging to Fusarium, Alternaria, Penicillium, Botrytis, and Rutstroemia genera. Particularly, the strains which inhibited growth of F. equiseti were identified as B. cereus, B. mojavensis, B. velezensis, B. subtilis and B. amyloliquefaciens by sequencing rpoB gene. The strains were further characterized for the presence of cyclolipopeptides (cLP) genes (fenD, bmyB, spaS, dfnM, ituA, mycA, srfAA), genes encoding plant-induced resistance factors (ysnE, yxvQ, beta-Glu), and for the production of lipopeptides (iturins, fengycins, surfactins), indoleacetic acid, siderophores, hydrocyanic acid, extracellular enzymes (amylase, protease, pectinase, cellulase) and phosphate solubilization. Hierarchical and correspondence analysis showed the clustering of Bacillus strains into three different groups, where the strains with the highest antifungal activity are correlated to the presence of different biosynthetic genes and production of broad spectra of metabolites. They include strains of B. amyloliquefaciens, B. velezensis, B. subtilis and B. mojavensis. Furthermore, these strains showed high levels of Fusarium wilt reduction in V. faba under greenhouse conditions, as well as they have shown plant promoting activity.

Automated summary

Bacillus strains have shown potential in controlling fungal infections in Vicia faba, with certain strains exhibiting high antifungal activity and being classified based on biosynthetic genes and metabolite production. These strains have demonstrated effective control of Fusarium wilt in V. faba and have shown plant growth-promoting activities.