Leila Sahampoor - Plant Biotechnology, Higher Education Complex of Shirvan, Shirvan, Iran.
Fatemeh Zaker Tavallaie - Plant Biotechnology, Higher Education Complex of Shirvan, Shirvan, Iran.
Seyed Reza Fani - Plant Protection Research Department, Yazd Agricultural and Natural Resources Research and Education Center, AREEO, Yazd, Iran.
Samira Shahbazi - Plant Protection Research Department, Nuclear Science and Technology Research Institute (NSTRI), Atomic Energy Organization of IRAN (AEOI), Karaj, Iran.

Trichoderma is very important as a bio control agent and probably a good alternative for chemical fungicides. Fusarium oxysporum is a plant pathogen that causes wilt in a wide range of plants. The use of gamma irradiation can be employed to increase Trichoderma efficiency against F. oxysporum. The induced mutation provides genetic changes in Trichoderma and in some of the mutated isolates the efficiency of bio control may be improved. In this study the efficiency of mutated T. harzianum CS۵ against the F. oxysporum f.sp. radicis-cucumerinum was evaluated. Among ۱۶ wild isolates of Trichoderma, CS۵ isolate was chosen based on synchronous and nonsynchronous mutual cultivation with pathogen. The spore suspensions of T. harzianum CS۵ were irradiated in a cobalt- ۶۰ γ- irradiator at a dose rate of ۰.۲۳ Gy/Sec in Nuclear Agriculture Research School, (NSTRI, AEOI). Then antagonist screening of ۷۶ mutants was investigated in the experiments of synchronous and nonsynchronous dual culture with pathogen. The results showed that only ۱۷ mutants were able to control the pathogen better than wild type, and YFTM۸۰ isolate had the most prevention. Using the ERIC-PCR marker, the distinction was investigated between the wild type and the ۱۷ selected mutants. The results showed that the gamma ray is able to improve biocontrol efficiency of Trichoderma and the ERIC-PCR marker can differentiate among derived mutants, but it does not have the ability to distinguish mutants from wild type. In terms of antagonistic superiority, mutations might have occurred in antagonistic sites, which have led to improved antagonistic efficiency. Probably the ERIC-PCR marker has failed to replicate these areas.

Trichoderma, Gama ray, Mutation, Fusarium oxysporum f. sp. radicis-cucumerinum