Antifungal activity and bean growth promotion of Trichoderma strains isolated from seed vs soil

The common bean is a legume crop distributed worldwide. Dry bean production has gone through increasing difficulties due to relatively low yields in the last few years. Rhizoctonia solani is one of the root and hypocotyl pathogens that causes most of the economic losses in this crop. One promising strategy to control plant diseases is the use of biological control agents, able to reduce the negative effects of pathogens and to promote positive responses in the plant. Trichoderma spp. is a fungal genus ubiquitous in soil that can grow in soil or in any of the above ground parts of plants. The aims of this work were to study the effect of Trichoderma on bean plant growth, in the presence of the phytopathogen R. solani , according to the Trichoderma isolation source (seed or soil). Fifty-five Trichoderma isolates collected from bean seeds and from bean field soils were analyzed. Among them, those isolated from soil samples showed a higher plant growth promotion activity than those strains isolated from seeds , in the presence of R. solani. Furthermore, bean plants inoculated with Trichoderma -soil isolates showed a higher percentage of germination, hypocotyl diameter, length of the root system, and dry weight of aerial parts and root system than plants inoculated with Trichoderma- seed isolates.