COMPETITION FOR CELLULOSE EXPLOITATION BETWEEN RHIZOCTONIA SOLANI AND TWO TRICHODERMA ISOLATES IN THE DECOMPOSITION OF WHEAT STRAW
S. Sarrocco, L. Guidi, S. Fambrini, E. Degl’Innocenti, G. Vannacci
The competitive saprophytic ability (CSA), expressed as competition for wheat straw, between Rhizoctonia solani and two antagonistic strains of Trichoderma (T. virens I10 and T. asperellum I252) was evaluated. Both antagonists competed with R. solani for wheat straw possession for up to 10 days. Later, straw baits were occupied by R. solani, but the rates depended on the antagonist present. Cellulolytic activities were evaluated as a possible mechanism for maintenance of the resource, since the major components of wheat straw are cellulose and hemicelluloses. Mycelial protein content was used to estimate fungal growth, with sucrose or straw as the only carbon source. R. solani grew equally well with sucrose or straw, whereas the antagonists did better on straw. Levels of extracellular proteins produced by the three isolates changed with the carbon source, being highest in straw for all fungi tested. Among the enzymatic activities tested, only cellulase activity of T. virens I10 decreased with time and this correlated with reduction in competitive ability. We conclude that efficient exploitation of cellulose plays a role in competition for straw.