The process of antagonism of Sclerotium cepivorum in white rot affected onion roots by Trichoderma koningii

Trichoderma koningii (strain Tr5) grew in the epidermal mucilage of onion r oots without entering healthy epidermal tissue. When placed on the epidermi s of Sclerotium cepivorum-infected roots, T. koningii colonized epidermal p assage cells, with little colonization of other epidermal tissues, then bra nched and spread throughout the root cortical tissues damaged by enzymes an d toxins which diffused ahead of S. cepivorum hyphae, and impeded the path of the infection. When T. koningii colonized infected tissue, many S. cepiv orum hyphae became detached at septa, cell walls dissolved and many hyphal apices burst. Contact between hyphae was not necessary for lysis to occur. T. koningii produced two endochitinases (R-f 0.15 and 0.24) and two exo-act ing chitinolytic enzymes (R-f 0.46 and 0.62) during degradation of crabshel l chitin and S. cepivorum cell walls. The R-f 0.24 and 0.46 proteins were d etected when T. koningii colonized S. cepivorum-infected roots and are, lik ely to be a component of the antagonism process.