| Evaluation of wheat mutants for days to maturity A.S. LARIK, K.A. SIDDIQUI1, H.M.I. HAFIZ2 and M.H. ARAIN Depatrment of Plant Breeding and Genetics, Sind Agriculture University, Tandojam, Pakistan. Physical and chemical mutagens are know to induce earliness or lateness in crop plants. According to a recent estimate about one third of the mutant varietites evolved so far carry gene(s) for earliness or lateness. Altering flowering or maturity time by genetic means such as mutation induction, must always involve interference with one of the control mechanisms such as vernalization requirement, day length reaction or temperature sensitivity. Also, day length neutrality has been created by mutation induction and it can be suspected that many of the earlier or later mutants reported in fact have an altered day length response (MICKE 1979). It is therefore necessary to evaluate newly eovolved strains or mutants under different environmental conditions. We selected nine mutants out of forty two phenotypically stable mutants reported earlier (SIDDIQU 1972) for detailed study of longevity measured in terms of days to maturity. Earthen pots measuring 22 x 20 cm were filled with 2.5 kg of air dried loamy soil, irrigated with 500 ml of tap water one day before sowing. The amount of mineral nutrients per pot was calculated equivalent to the field rate on soil weight basis (54 kg N, 27 kg P2O5 and 13.5 kg, K2O per acre). The full dose was applied by thorughly mixing it in the soil of each pot before irrigating the soil for sowing. Twelve seeds per pot of 13 cultivars were planted at 2 cm depth with marked glass rod. The experiment was planned with complete randomized design having five repetitions. Detailed chemical and mechanical analysis of soil is reported earlier (LARIK et al, 1983). Analysis of the mutants revealed that mean heading and maturity days of EMS-derived mutants significantly shifted towards earliness whereas, mutants originating from gamma rays treatments displayed highly significant lateness (Table 1). Mutant-7 of C-591 took significantly (P>=.01) lesser time from heading to maturity as compared to its mother cultivar. Such early mutants have also been reported by other workers (GUSTAFSSON et al. 1960 ; EL-HATTAB & IBRAHIM 1970 ; IBRAHIM & SHARAAN 1974). Hexaploid wheat, which apparently has a good amount of its genes in triplicate as evidenced by 7 homoeologous grous, presumably has a vast reservior of loci that can be mutated in various ways without being detrimental to the plant. Thus, early types and specificity in action at certain loci in EMS-derived mutants can all be due to the ability of EMS to induce functional alteration in the genes. |
| 1 Head, Plant Genetics Division, Atomic Energy Agricultural
Research Centre, Tandojam, Pakistan. 2 Department of Botany, New Campus, Punjab University, Lahore-20, pakistan. |
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