Abstract: The effects of gamma irradiation doses on spore germination of Trichoderma harzianum and its effects on morphological variation and antagonistic capability of the mutants to control Rhizoctonia solani were evaluated. Spore suspension of Trichoderma has been gamma irradiated with 0, 50, 100, 150, 200, 250, 300, 350, 400 and 450 Gry in Nuclear Agricultural Research School (Nuclear Science and Technology Research Institute, Karaj). Gamma ray effects on mycelial growth were evaluated by irradiation with 0, 400, 800, 1200, 2000 and 2500 Gry. The results showed that the 450 Gry gamma radiations completely blocked the spore germination and 250 Gry was the optimum dose to induce mutation in Trichoderma. Furthermore, gamma irradiation could change the morphological characteristics such as colony shape and color, sporulation and mycelia growth rate. The dual culture test showed that the mutated isolates have statistically higher antagonistic capability against R.solani than their parent strain. According to these results, the bio-control capability of Trichoderma could be improved through the gamma radiation.

Keywords: Gamma radiation, Mutation, Biological control, Trichoderma harzianum, Rhizoctonia solani
J. of Nucl Sci. and Tech 71