Biocontrol of Rhizoctonia solani infection in common bean ( Phaseolus vulgaris ) by Trichoderma species from northwestern Argentina

Aims To evaluate the biocontrol of Rhizoctonia solani fungal infection in common bean (Phaseouls vulgaris) by using native Trichoderma spp. from northwestern Argentina. Methods and results Eight Trichoderma isolates were assessed for their ability to inhibit AG4 R. solani growth through dual culture. All Trichoderma isolates suppressed fungal growth at 4 days post-inoculation, and completely overgrew on it by exerting high antagonism. Mainly, T. afroharzianum isolates (Th15, Th45 and Th51) reduced the root rot severity (42-51%) in white common bean (cv. Alubia), and increased the germination index, fresh weight, and root lengths in bioassays (inoculated and non-inoculated with the pathogen). Conidial suspensions of T. afroharzianum isolates (Th15, Th28 and Th51) decreased R. solani infection by 30-50% in white common bean seedlings and increased stem and root development in greenhouse assays. Moreover, liquid culture of T. afroharzianum Th15 also showed antifungal activity on the growth and infection of R. solani in black common bean (cv. Leales 15). Th15 colonization competed effectively with R. solani by reducing the disease severity index and the inoculum of R. solani in bean roots (the latter of which was assessed by qPCR). Conclusions T. afroharzianum Th15 is a biological agent with the potential to protect two cultivars of common bean from the pathogenic attack of R. solani.