| Aneuploid analyis for resistance against stem rust
race 21 in wheat variety Kalyansona D. SINGH*, B.C. JOSHI*, L.B. GOEL*, M.K. MENON+ and P.N.N. NAMBISAN+ Indian Agricultural Research Institute, New Delhi, India. Up until 1954, when SEARS reported the production of a complete series of 21 monosomic lines in the hexaploid wheat variety Chinese Spring, all the studies regarding the inheritance of rust resistance were confined to conventional genetic analyses. In wheat, so far in all, 34 stem rust resistance genes have been indentified. By aneuploid analyses till to date, 29 different Sr genes (Sr=stem rust=black rust=Puccinia graminis Pers. f. sp. tritici Eriks & Henn) have been located on specific chromosomes of hexaploid wheat by various workers. In the present investigation, attempt has been made to locate rust resistance gene(s) on specific chromosome(s) of wheat variety Kalyansona against race 21 of stem rust. Materials and Methods Wheat variety Kalyansona was selected for locating gene(s) conditioning seedling resistance against stem rust race 21. Race 21 is one of the most prevalent races of stem rust in India. For this purpose monosomic analysis was employed. The 21 monosomic lines of wheat variety PbC591 used were developed by SWAMINATHAN et al. (1968). Monosomic (2n=41) Plants were identified cytologically in all the 21 aneuploid lines of PbC591 and were crossed with Kalyansona. F1 progenies were grown and monosomic F1 hybrids were identified in all the 21 lines. F2 seeds were collected from the monosomic F1 hybrids and grown in the glass house for testing against race 21 of stem rust. To serve as control, PbC591 (2n=42) was crossed with Kalyansona, the F1 progeny grown and F2 seeds collected for testing against stem rust race 21. The F2 seedlings were raised and inoculations were carried out with the stem rust race according to the technique described by STAKMAN et al. (1944). Observations were recorded on the infection type 15 to 25 days after inoculation and classified according to the scale devised by STAKMAN et al. (1962). The tests were carried out at a temperature ranging from 8C to 22C. A chi-square test was applied to the segregation ratios of the resistant and the susceptible plants obtained in the F2 generation of the control cross and after selfing the monosomic F1 hybrids, after infecting with the rust race. The control cross provided the data of the conventional genetic analysis and among the F2, derived from the monosomic F1's, only those lines which deviated from the expected ratios were considered to be the critical lines (chromosomes on which the resistance genes are located). |
| * Division of Genetics, Indian Agricultural Research Institute, New Delhi.
+ Regional Research station of Indian Agricultural Research Institute, Wellington (Nilgiris), Tamil Nadu. |
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