In vitro antagonism of Trichoderma harzianum on Sclerotium cepivorum Berk. and S. rolfsii Sacc., causal agents of onion rot

In vitro tests were carried out, to evaluate the antagonistcapacity of a strain of Trichoderma isolated from soil in LaCienega de Chapala, Michoacan, Mexico against Sclerotium cepivorumand Sclerotium rolfsii, casual agents of onion rot, an importantdisease in Mexico and the rest of the world. Percentages of radialgrowth inhibition (PRGI) were calculated every 24 h, until a rateof antagonism was obtained according to the Bell’s scale, as well asthe percentages of inhibition of the production of sclerotia and theirparasitism. The PRGI was 17.4% against S. rolfsii and 22.2% againstS. cepivorum after 48 and 72 h, respectively. Trichoderma harzianumobtained a degree of antagonism of 1 on S. cepivorum and two againstS. rolfsii, on the Bell scale. On the other hand, T. harzianum reduced(P≤0.05) 95% the production of sclerotia of S. cepivorum and 78%that of S. rolfsii; the parasitism of the sclerotia of S. cepivorum and S.rolfsii was 91% and 54%, respectively.