Freezing stress as one of the abiotic stresses limits the plant growth in some areas. Therefore, increasing the tolerance to freezing stress is necessary for surviving in winter. Plant diversity can be produced by mutation in plant breeding programs. This research was carried out with the purpose of applying gamma-ray as a mutagen for screening freezing tolerant chickpea genotypes. At first, 50 percent of lethal temperature (LT50) of shoots after cold acclimation and freezing stress (0 to -20 o C) were determined by calculating the survival percentage. Then seeds of three chickpea genotypes were treated by different doses of gamma radiation (60, 100, 140 and 180 Gy) and the shoots were placed in their LT50 temperatures. The LT50 of three genotypes of MCC477, MCC495 and MCC741 were -11.5, -12.3 and - 12.5 o C, respectively. Significant differences were observed (P≤0.01) among doses and genotypes according to their survival percentage. The highest survival percentage, 80.1 and 64.6, were observed in the two genotypes of MCC741 in 180 Gy dose and MCC495 in 140 Gy dose, respectively. The increased survival of these two genotypes up to more than 50 percent, could show the increased tolerance to freezing. The radiation may effect the expression of genes which are responsible for freezing tolerance. The results of this experiment showed that gamma radiation can be a suitable strategy for obtaining the freezing tolerant lines in chickpea.

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