Abstract

In vitro studies with Trichoderma spp., soil-borne fungal antagonists, demonstrated
that a number of isolates produced volatile and non-volatile metabolites
capable of inhibiting the growth and sporulation of several soil-borne plant
pathogenic fungi. Microscopic observations showed that T. harzianm and T.
viride, isolated from soil samples from Ahwaz and Karaj, adversely affected the
mycelial growth of Rhizoctonia solani, the causal agent of seed, root rot and
damping-off of bean, by hyphal contact, coiling, penetration, necrosis, lysis and
in some cases fraginentation of the pathogen hyphae. T. harzianum hyphae
grew parallel to those of Phytophthora drechsleri, the causal agent of root rot of
cucumber, and produced appendages that attached themselves to P. drechsleri
hyphae. Isolates of T. harzianum from Ahwaz and T. viride from Shahriar ,
Karaj, significantly reduced the germination of pseudosclerotia of
Colletotrichum coccodes, the causal agent of brown stem, root rot and black dot
of potato. The Ahwaz isolate of T. harzianum inhibited mycelial growth and
germination of Phytophthora erythroseptica, the causal agent of pink rot of
potato tubers, without penetrating the pathogen hyphae. Trichoderma spp. also
reduced the mycelial growth and spore germination of Fusarium solani, the
causal agent of black root rot of chickpea