| Results and Discussion Among the plant characters associated with lodging and nitrogen responsiveness, plant height is predominant factor affecting lodging resistance (SCARASCIA-MUGNOZZA, 1970) and characters such as srtaw architecture exert an influence on polygenic traits like grain yield and protein quality (LARIK, 1978; SIDDIQUI & DOLL, 1972, 1979). It is therefore necessary to take into consideration all the related plant attributes in any meaningful genetic evaluation of wheat mutants. Studies are therefore conducted of the straw architecture and leaf characteristics. Analysis of variance for straw characters indicate that mutant genotypes differed significantly (P>=0.01) from common parental variety Nayab. Mean values of the characters associated with straw architecture are given in Table 2. Mutants 27 and 44 displayed reduction in plant height at 1 % level of significance. The first internode of mutants 27, 31 and 35 reduced significantly (p>=0.01) whereas, second and third internode length of all mutant strains increased significantly (p>=0.01) as a consequence of gamma irradiation. Semi-dwarf mutant genotypes has spectacularly increased the yielding ability of wheat due to increased resistance to lodging. In relation to photosynthesis - respiration balance, shorter culms may minimize respiration loss by the culm, thereby improving net grains. All the mutants produced highest yield (economic as well as biological yield) and high harvest index in comparison to the mother variety. This appears to be an additive effect of positive genes which has increased the grain yield in all the mutant genotypes. This also confirms the significant role of gamma radiation in improving grain yield of mutants. Using straw as architectural element, the plant height and other related characters of mutants were correlated with grain yield. Results in Table 3 reveal that in all mutants plant height Leaf Characters. The present investigation was confined to the morphological study of leaf characters of the mutants derived from Nayab cultivar. The results of analysis of variance (Table 1), showed highly significant (p>=0.01) differences amongst various genotypes which suggest that genotypes varied significantly for leaf characters. Mean values of the leaf characters are presented in Table 2. Data reveal that in all the mutants leaf characters did show slight improvement in the leaf length and breadth but not to the level of significance. Leaf length/ breadth ratio, which affect Carbon-Nitrogen ratio and ultimately the productivety in present studies also displayed some improvement in the mutant strains. These results are in good agreement with the results obtained by LARIK (1977) in mutants of wheat. |
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