Evaluation of Effect of Gamma Rays Irradiation for Increasing of Variation in Germination and Agronomic Traits in Oilseed rape (Brassica napus L.)

Increasing of genetic diversity is one of primary and basic goals of plant breeding programs. Induction of mutation is a method to increase genetic diversity that can be used in accommodate with selection, recombination and or combination of them in plant breeding. The aim of this study was to investigate the impact of different doses of gamma rays (500, 700, 900, 1100 and 1300 Gry) on primary growth characters, such as: rate and percentage of germination, the length of rootlet and stemlet in M1 generation, and on agronomic characters such as: plant height, number of lateral branches, number of pods on main and lateral stem, length of pods and weigth of 1000-seed in M2 generation for two varieties of oilseed rape (Brassica napus), PF and Zarfam. Results of lab experiments showed that for both varieties, the germination percentage, the length of rootlet and the length of stemlet were significantly decreased by mutagen in compare with the control. While germination rate was only significantly affected by mutagen in PF. The estimation of "F" showed that there was significant difference between the variance of treatments for the germination rate and germination percentage in PF cultivar and for germination rate and stemlet length in Zarfam cultivar. In fact, increasing of gamma doses causes considerable enhancement in variance of treatment in compare with the control. The maximum relative coefficient of variation was related to 1300 Gry for germination rate of PF. In M2, all traits of study except number of pods on main stem was decreased by different doses of Gamma rays in PF cultivar. In opposition to other traits, Pods on main stem in PF cultivar was increased in different doses of gamma ray in compare with the control. But in Zarfam cultivar, only 1000-seed weight was significantly affected by Gamma rays.