| Results and Discussion M1-generation : The effect of diethyl sulfate (DS) on mean performance of a pure line wheat cultivar (Hinta Madeni) for the grain yield and various yield components are presented in Table 1. The results showed that the treatment with the highest concentration (0.26%) and least time (30 minuts) caused an enhancement effect on genes controlling traits which reflected an increase in population means for all the triats studied. To some extent, treatment with lowest concentration (0.008%) and longest time (24 hours) came up with similar trend for all traits except the number of spikes per plant. In contrast, treatments with highest concentrations and longest times, i.e. 0.26% DS+1 hour and 0.02% DS and 24 hours, resulted in a reduction in the mean values of most traits. This reduction in means may be due to detrimental mutations which occur more frequently than favourable ones. WILLIAMS & HANWAY (1961), BOROJEVIC (1966) and SIDDIQUIet al. (1981) found negative shifts in the population mean due to mutagen treatments. KASSEM et al. (1976) found that EMS resulted in significant reduction in the mean of grain yield, kernels/spike and kernel weight of Sonora 64 and means of kernel weight of Giza 150. M2-generation: a. Analysis of variance : Mean squares of different traits studied in M2 generation are presented in Table 2. The results showed that M2 lines under M1sel ected categories, i.e. types of SS. GH and levels of high (H), medium (M) and low (L) activated or induced by diethyl sulfate (DS) showed highly significant differences for all traits studied. In general, it can be concluded that the higher frequencies of positive and negative mutants were found to be distributed in the early M1 generation. NAYAR & NINAN (1978) came up to similar conclusion in rice. On the other hand selection types i.e. (SS) spike length and spikelets per spike ; and (GH) grain yield and harvest index, revealed significant differences for grain yield and number of spikes per plant while the other traits were insignificant. It can be concluded that selection levels within each type was more pronounce than selection of types itself. These results are in agreement with those obtained among (SS) and (GH) levels, hence highly significant differences were obtained for all traits except the number of spikes/plant (among SS) and number of kernels/spike (among GH). It can be concluded from these results that the effect of mutagen (DS) under two M2 types and selection levels within both types, in positive and negative directions, was highly significant. Consequently, disruptive selection successed in distinguishing various levels in each type. Comparing the selected type (SS) with the control showed highly significant differences (1% level) for grain yield, number of spikes/plant ; and significant differences (5% level) for the remaining traits. While the other type (GH) vs. the control showed insignificant differences for all traits except the 100-kernel weight. |
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