| An unusual rate of transmission of double monosomics
in wheat B. C. JOSHI Division of Botany, Indian Agricultural Research Institute, New Delhi-12, India The monosomic lines of wheat variety Chinese Spring, developed by E. R. SEARS, are being maintained at the Indian Agricultural Research Institute, New Delhi, for utilizing them for genetic analyses. In the course of a four year study it has been observed that the frequency of double monosomics (19II+2I) that have been recorded from among the monosomic (20II+1I) progenies is very high (Table 1), as compared with the reports available in the literature. Frequency in per cent is given in parentheses PERSON (1956) in a study of 225 monosomic progenies found only one double monosomic plant and Mc GINNIS and CAMPBELL (1960) have also reported a similarly low frequency (0.4 per cent). As compared with this the observed mean frequency of 3.0 per cent double monosomics in the present study is significantly higher and in fact corresponds to the expected frequency of nullisomics (20II) that are expected on selfing monosomics. No definite explanation can be offered to explain this unusual transmission of double monosomics. It is possible that differences in temperatures existing at different locations may be responsible for this as has been reported by RILEY (1966) with respect to chromosome pairing in nulli-5 D tetra-5 B material grown at different temperatures. (Reccived Oct. 12, 1966) Literature CitedPERSON, C. 1956. Can. J. Botany 34: 60-70 MC GINNIS R.C. and A. B. CAMPBELL, 1960. Can. J. Genet. Cytol. 2: 47-56 RILEY, R. Chromosomes Today, 57-65, Oliver & Boyd, Edinburgh and London |