INFLUENCE OF BEAN SEEDLING ROOT EXUDATES ON THE RHIZOSPHERE COLONIZATION BY TRICHODERMA-LIGNORUM FOR THE CONTROL OF RHIZOCTONIA-SOLANI

Application of Trichoderma lignorum as a seed coating (8 x 10(6) conid ia/seed) or wheat bran preparation (1 x 10(6) cfu/g) at a rate of 20 g /kg soil, greatly reduced the number of bean seeds infested by Rhizoct onia solani, and the percentage of healthy seeds reached 92%. Germinat ion of conidia of Rhizoctonia solani in bean rhizosphere soil was inhi bited after soil or seed application with Trichoderma lignorum. Bean s eedling exudate increased the mycelial growth rate of Rhizoctonia sola ni and Trichoderma lignorum in vitro. Under greenhouse conditions, the addition of germinating bean seed exudate to soil infested with Rhizo ctonia solani and planted with bean, reduced the disease control capab ility of the antagonist. Plants grown from seeds treated with Trichode rma lignorum had roots with lower levels of Rhizoctonia solani in thei r rhizosphere than the roots of untreated seeds. Trichoderma had littl e effect on the survival of Rhizoctonia solani in non-rhizosphere soil . However, application of Trichoderma lignorum as a wheat-bran prepara tion, conidial suspension or seed coating reduced the pathogen counts in the rhizosphere soil of beans.