Biological control of chickpea seed-rot and damping -off caused by Pythium ultimumwas studied , using an antagonistic fungus (Trichoderma harzianum) isolated from the soil of a chickpea field in Karaj and two other isolates received from the College of Agriculture, Karaj. In laboratory tests Trichoderma harzianum, T. viride and Gliocladium virens were tested for nutrition competition and colonization in double culture method on PDA againsts Pythium ultimwn. The effects of volatile and nonvolatile compounds of these antagonists were very different. T.viride and G.virens had very strong mycoparasitism effect on the pythium , but their antibiosis effects were weak, T.haizianum had diverse activities .Isolates of T.viride and G.virens were used in the field trials. In these tests , the antagonists at the rate of 1-5x107 spores/seed Metalaxyl 25% (0.3gr. / Kgr.seed) was used for seed treatments .Seeds were planted in the field (of Agricultural College in Karaj) . The soil was inoculated with Pythiwn by 2000 propagules per gram. This experiment was carried out with 4 replications in completely randomized block design and included infected and natural controls. 27 days after seedling emergence, percentage of seed germination was counted, The results indicated G.virens, T.viride and Metalaxyl treatments were highly significantly different than the inoculated control.
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