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Genetics of dwarfing and awning by monosomic analysis
in wheat variety Mex. C.B. 116 N. C. SINGHAL, M. P SINGH, C. S. KALIA Genetics Division, Indian Agricultural Research Institute, New Delhi-12, India In order to locate the gene (S) for dwarfing and awning on a particular chromosome, the wheat variety Mex. C.B. 116 was crossed with all the 21 identified monosomic lines of Chinese Spring. The F1 plants of all the monosomic progenies were screened for awning and height. The results obtained on the expression of awning are summarised in Table 1. The variety Mex. C.B. 116 is derived from the cross (Nai 60 x TT-64) x (L.R. x Son. 64). The variety seems to have partial dominance effect, as in F1, all the plants were showing tendency to appear more towards dwarf parent. Chromosome 6D of Mex. C.B. 116 seems to carry genes for dwarfing, as maximum manifestation of dwarfing was observed. Mex. C.B. 116 is a fully bearded type (mean awn length 7.76 cms), while Chinese Spring is awnless. All the F1's monosomic plants were identified on the basis of their chromosome number, 2n =41. Depending on awn expression the F1 plants were classified as fully bearded (F.B), half bearded (H.B), long tipped (L.T), tipped (T) short tipped (S.T) and awnless (A.L), Table 1. The identified monosomic plants were selected and their comparison was done with their respective disomics. Normal crosses between Chinese Spring x Mex. C.B. 116 showed tipped awn expression in F1, thereby indicating a partial dominance of awnless condition. Monosomic F1 plants of 6B line were having maximum phenotypic manifestation of awning (6.05 cms) and monosomic plants in line 4B showed half bearded nature of awning. It thus became obvious that variety Mex. C.B. carried recessive genes b1 and hd on chromosome 6B and 4B respectively. In the absence of dominant awn inhibitors B1 and HD of Chinese Spring (Sears 1954), the recessive gene (S) contributed by Mex. C.B. 116 give expression to awning, though the expressivity is reduced. Significant increased awning in monosomic plants in line 3A, 1D, 3D and 5D could possibly be due to presence of awn promotor genes. It was interesting that the line 5B and 6D showed almost an awnless condition. Similar observations were recorded, when variety Hira was crossed with Chinese Spring monosomic lines (SINGHAL and SINGH unpublished). Exact genetics of dwarfing and awning will be discussed in more details after critical analysis of F2 populations. Acknowledgements Our thanks are due to Dr. H. K. JAIN for his interest and to Dr. E. R. SEARS for providing the Chinese Spring monosomic material. Literature cited SEARS, E. R. 1954. The aneuploids of Common Wheat. Research Bulletin University of Missouri. SINGHAL, N. C. and M. P. SINGH, under publication 1973. (Received February 2, 1973) |