| Gamma originated mutants displayed lateness in heading and maturity time
(Table 1). This shows that gamma irradiation causes
deeper physiological damage before reaching lethality (MOES 1963). SWAMINATHAN
et al. (1962) after an extensive study with wheat and barley concluded
that in evolution of gene placement along the chromosome arms it is likely
that linkage groups in which geness without need for recombination are located
near the centromere would have had a selective disadvantage. The location
of genes relating to earliness in the proximal segments and the high susceptibility
of such regions to EMS action may perhaps be factor involved in the induction
of a large number of early mutants in EMS-treated material. Data from linkage
analysis in barley (ROBERTSON 1963 ; NILAN 1964) and studies on chromosomal
aberration aberration (NATARAJAN & UPADHYA 1964) have provided eivdence
in support of this view. Association of heading and maturity with grain yield was also estimated. Heading was strongly associated (r=.98**) with maturity. The relationship of these traits with grain yield was positive but not significant. However, earliness was accompanied by high yielding capacity of EMS induced wheat mutants compared to their mother cultivar (GAUL 1961 ; GUSTAFSSON 1963 ; IBRAHIM et al. 1966). All the early and late mutants produced higher grain yield than the respective mother cultivars. However, only mutant-22 derived from Nayab produced significantly (P>=.05) higher yield than the mother cultivar. The present study suggests that EMS is efficient in inducing earliness in wheat, likewise gamma rays appear to be a suitable mutagen for inducing lateness. The chioce of strategy would depend on the objectives of a particular plant breeding programme. Literature Cited EL-HATTAB, H. and A.F. IBRAHIM. 1970. Genetika 2 : 131-140. GAUL, H. 1961. In : Mutation and Plant Breeding, NAS-NRC 891 : 206-251. GUSTAFSSON, A. 1963. Hereditas 50 : 211-263. GUSTAFSSON, A., HAGBERG and U. LUNDQVIST. 1960. Hereditas 46 : 675-699. IBRAHIM, A.F. and A.N. SHARAAN. 1974. Z.Pflanzenzuchtg 73 : 47-57. IBRAHIM, A.F., G. ROBBELEN, A. SCHEIBE and M.ZOSCHKE. 1966. Ibid. 56 : 251-284. LARIK, A.S., K.A. SIDDIQUI. H.M.I. HAFIZ and M.H.ARAIN. 1983. Genetica Agraria (in press) MICKE, A. 1979. Gamma Field Symposia 18 : 1-23. MOES, A. 1963. Proc. Ist. Int. Barley Genet. Symp. Wageningen 82-91. NATARAJAN. A.T. and M.D. UPADHYA. 1964. Chromosoma (Berl) 15 : 156-169. NILAN, R.A. 1964. Monographic Suppl. 3, Washington State Univ. 32 : 1-278. ROBERTSON, D.W. 1963. Proc. Ist. Int. Barley Genet. Symp. Wageningen, 159-167. SWAMINATHAN, M.S. ; V.L. CHOPRA and S. BHASKARAN. 1962. Ind. J. Genet. 22 : 192-207. |
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