| Identification of chromosomes carrying factors for
seed storage proteins M. P. JHA, A. K. KAUL, P. RAGHAVIAH and M. S. SWAMINATHAN Atomic Energy Lab., I.A.R.I., New Delhi-12, India The necessity and feasibility of improving the protein content and its quality in wheat have been stressed by SWAMINATHAN(1) and BORLAUG(2). As high as 20% Protein has been recorded in wheat (JOHNSON et al.(3) and AUSTIN et al.(4)). BORLAUG(2) and JOHNSON et al.(3) have shown that higher protein quantity of superior quality can easily be incorporated in high yielding strains of wheat through hybridization in widely divergent genotypes. Since a knowledge of the genetics of protein characters would be helpful in breeding, an attempt was made to identify the genes associated with high protein content and to locate the same on specific chromosomes through monosomic analysis. Each of the twenty-one monosomic lines of the wheat variety Chinese Spring was crossed with the dwarf varieties Sonora-64 and Lerma Rojo-64A. As against a 12% protein content in the disomic variety Chinese Spring, Sonora-64 and Lerma Rojo contained about 15% Protein at the same soil fertility level. The monosomic Chinese Spring lines were used as female parents and Sonora-64 and Lerma Rojo as male parents in the two separate sets of crosses. The protein content was determined for 42 chromosome and 41 chromosome plants in all the 21 monosomic lines in the F1 generation. The F2 populations derived from the monosomic F1 plants, for each monosomic line, were harvested in bulk. Seeds from some randomly chosen single plants from each of the 21 lines were harvested separately. The F3 progenies of twenty single F2 plants for critical monosomics were raised and their grain protein content was also determined. The Dye binding capacity technique (UDY(5) and KAUL et al.(6)) was used to determine the protein quality in the 1968-69 material. Tryptophan content of the critical chromosome lines showing high protein content, was also determined along with their parental lines (SPIES and CHAMBERS 1949). The 21 monosomic lines of Chinese Spring did not differ significantly in protein content among themselves. However, in comparison to the disomic the grain protein content in each of the 21 monosomic lines was slightly higher (Table 1). The monosomic F1 plants of eight chromosome lines namely 1D, 2A, 3A, 3B, 5A, 6B, 7A and 7B in Chinese Spring x Sonora-64 showed a significantly higher grain protein content in comparison to their disomic counterpart (Table 2). Similar significant increases in grain protein content were observed in the monosomic F1's of five chromosomes-1D, 3A, 3B, 6B and 7D in Chinese Spring x Lerma Rojo. The F2 data for two seasons (1967-68 and 1968-69) showed a significant increase in grain protein content in the F2 progenies of 41-chromosome F2 plants for six chromosomes, namely 1D, 3A, 3B, 5A, 7A and 7B in Chinese Spring x Sonora-64. In two chromosome lines involving 2A and 6B, an increase had been observed in the F1 monosomics, but no corresponding increase in grain protein content could be obtained in the F1 progenies. In Chinese Spring x Lerma Rojo, a highly significant increase in grain protein content was observed in the F2 progenies of 41-chromosome F1 plants involving chromosomes 1D, 3A, 3B and 7D. The high grain protein noted in the 41-chromosome F1 plants for 6B, however, was not maintained in the F2 progenies. In monosomic F1's of 2A and 6B in the Sonora-64 cross and 6B in the Lerma Rojo cross there was shrivelling of seeds and partial sterility and these could account for some of the enhanced protein content observed in them. In F1, the grain protein content was higher than the mid-parent values in both the crosses. In the critical monosomic lines also, protein content was higher than that in the donor parent (Lerma Rojo and Sonora-64). This may be due to a heterosis effect for protein content. Sonora-64 and Lerma Rojo showed a significantly higher tryptophan content in comparision with Chinese Spring. The data on the tryptophan analysis (Table 3) showed a significantly higher tryptophan content in all the critical lines possessing a higher protein content in both F1 and F2 (i.e., monosomics 1D, 3A, 3B, 5A, 7A and 7B; and 1D, 3A, 3B and 7D in Chinese Spring x Sonora-64 and Chinese Spring x Lerma Rojo resspectively. |
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