The mutability induced with different gamma irradiation frequencies viz 15,25,35 and 45Krad doses in some agronomic and morphological traits of five divergent genotypes of wheat namely Pak-18, Pirsabak-85, Khyber-87, Pirsabak-91 and Inqilab-91 were studied in M1, M2 and M3 generations during rabi 1995-96, 19996-97 and 1997-98. These investigation were carried out in the research area of department of plant breeding and Genetics, Faculty of Agriculture, Gomal University of, Dera Ismail Khan. The characters included in these st5udies were germination percentage, days taken to earing initiation, days taken to earing completion, plant height(cm), number of tillers plant-1 ,spike length (cm) number of spikelets spike-1 , number of grains spike-1 , grain weight spike-1, 1000-grain weight and grain yield plant-1. The experiments were laid out in R.C.B.D having four replications with split plot arrangement with varieties in main plots and gamma rays doses in sub-plots. All the cultural operations were kept constant and uniform in all the treatments during all three years. The data were recorded from ten randomly selected plants form each treatment and analyzed statistically to established the level of significance among the treatment. The relationship of grain yield and ten agronomic traits through correlation and path co-efficient analysis was also established in present investigation.
The results showed that a wide range of variability / mutability exists in almost all the characters due to the effects of gamma rays/genotypes and their interaction. Highly significant differences in the mean values were obtained due to various radiation doses for all characters under study. The results indicated that in all generations(M1, M2 and M3) the effect of higher radiation doses(25,35 and 45Krad) on all characters were depressive, while the effect of 15Krad dose was stimulative on earing time, spikelets, grain spike-1 and 1000-grain weight. Highly significant differences in the mean values due to varieties were obtained for germination percentage, days taken to earing initiation and completion, pant height and number of grains spike-1 in M1 and M2 generations, spike length and number of siekelets spike-1 in M3 generation, grain weight, 1000-grain weight and grain yield plant-1 in M2 and M3 generations. Significant differences in the mean values were recorded for spike length in M1 and M2 generations and number of siekelets spike-1 in M1 generation , while non-significant differences in the mean values were recorded for number of tillers plant-1in M2 generation, grain weight spike-1, 1000-grain weight and grain yield plant-1 in M1 generation. All the five genotypes responded differently to radiation doses for some of the plant characteristics.
The interaction between radiation doses and varieties were also highly significant for almost all the characters. While, Significant differences in the mean values were obtained for germination percentage in M3 generation and non-significant differences in the mean values for spike length in M1 and M2 generations, spikelets spike-1, grain weight spike-1, 1000-grain weight and grain yield plant-1 in M1 generation.
The results of M1, M2 , M3 generation of genotypic and phenotypic correlations revealed that grain yield had a positive and highly significant relationship with germination percentage, plant height, numbers of tillers plant-1, number of spikelets spike-1, number of grain sipke-1 and 1000-grain weight. Spike length had a positive and highly significant correlation in M1 and M3 generations, while in M2 generation it was found to have a positive and significant correlation. The grain weight spike-1 had a positive and highly significant correlation in M1 generation and positive and significant correlation in M2 and M3 generations. Rest of the traits including days taken to earing initiation and completion was found to be negatively correlation in all the generations. The environmental correlation of grain yield plant-1 association with all others characters was non-significant in all the generation.
Regarding path analysis its was observed that germination percentage in M1, days taken to earing initiation in M1 and M2, days taken to earing completion in M3 , plant height in M2 and M3 number of tillers plant-1 in M1 and M2 , spike length in M2, number of spikelets spike-1 in M2 and M3 , number of grain spike-1 in M3, grain weight spike-1in M1 and M2 and 1000-grain weight in M1 and M2 generations had a positive direct effects on grain yield.