| Monosomic analysis of yield and yield components in
wheat cultivars N.C. SINGHAL and M.P. SINGH Division of Genetics, Indian Agricultural Research Institute New Delhi, India Through substitution lines, the genes responsible for quantitative characters have been located in specific chromosomes (KUSPIRA & UNRAU 1957; HERMSEN 1963; LAW 1967). Though the monosomic analysis is not very precise, but the results obtained were similar to the substitution lines (PETROVIC 1979). To ascertain the contribution of individual chromosome in the expression of yield and yield components, two varieties having diverse dwarfing source were selected. Through 'F2' monosomic analysis, the chromosome location of genes associated with yield trait were established. The data thus obtained is presented here and the results are discussed in the light of earlier observations. Materials and Methods The triple dwarf wheat genotypes (Triticum aestivum). Mex. C.B. 116 (Pedigree-Nai 60 x TT-Son. 64 x (LR x Son. 64) and Hira (Pedigree-E5477 x Son. 64) were crossed as a donor parents with all 21 identified monosomic lines of Chinese Spring and also with the normal disomic. The F1 plants were grown in the field and the monosomics were confirmed at meiotic metaphase. The identified monosomic F1's were selfed. The progenies from selfed monosomic F1 plants, and F1 plants from normal cross were subsequently sown in a randomised block design with three replications. The material was sown in two seperate sets, one comprised of 22 F2 populations derived from the crosses of Mex. C.B. 116 with 21 monosomic and one disomic Chinese Spring, and the other consisted of 22 F2 progenies of crosses with variety Hira. The observations were recorded on an individual plant basis and for that 40 plants were randomly selected from each plot. The means of different characters were determined per plot and the usual "F" test was applied to ascertain the differences between populations. The mean of parents were not included in statistical analysis. The F2 population derived from the crosses involving identified monosomic lines have been referred as 'F2' monosomic population. Results and Discussion The data pertaining to "F2" monosomic populations derived from crosses involving Mex. C.B. 116 and Hira for mean grain yield per plant and other yield components have been summarised in Table 1 and Table 2 respectively. The results have indicated that absence of a single chromosome does not significantly alter grain yield in both the varieties, Mex. C.B. 116 and Hira. These observations have a supporting evidence from the earlier report of JOSHI & SINGH (1968). However, their studies were limited to eight monosomic lines where they recorded no difference in grain yield between monosomic and disomic populations. Furthermore, yield is a complex character and is considered the ultimate product of the action and interaction among a number of quantitative characters, which are known to be controlled by different sets of polygenes. Therefore, some workers have even doubted the individuality of this character and have raised a point, whether there are any genes governing the yield per se (GRAFIUS 1959; KOHLI 1973). |
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