| Induced genetic variability in some dwarf wheat mutants
C.S. KALIA, M.P. SINGH and C. RAJLAKSHMY Division of Genetics, Indian Agricultural Research Institute, New Delhi-110012, India Wheat is one of the most important cereal crops in which dwarfing genes have considerably contributed for higher yields in the last two decades. Therefore, in this context induction of dwarf mutants in high yielding tall varieties have great practical importance. The stiff straw mutants have been recorded in many wheat varieties after physical and chemical mutagenesis (SINGH et al. 1985). Short coleoptile in dwarf and semidwarf varieties are primarily responsible for the poor seedling emergence under dryland farming condition. In the course of present investigations, efforts were made to evaluate the dwarf mutants with better yield potentials and to ascertain the relative range of coleoptile length for further selection. Material and Methods The hexaploid wheat variety NP 880 (6x) was subjected to varied chemical mutagens, consisting of three distinct groups of Aziridines, Nitroso compounds and Esters. The chemical mutagens used were Metapa (0.4% and 0.2%), Thiotepa (0.2% and 0.01%), MNG (0.1% & 0.05%), MMS (0.1% & 0.05%) and EMS (0.1% & 0.05%) in direct and sequential treatments. M1 was raised and bagged to ensure 100% self pollination. Each single plant was harvested and progenies were raised to select the M2 variant plants. Dwarfs were selected from tall NP 880 and their performance was studied in M3 and M4 generations. The yield contributing traits, spike length, spikelet number and seeds per spike were separately recorded for primary and secondary spikes. Results and Discussion The macromutants which were identified and separately harvested in M2 were sown as single plant progeny in M3 for checking their breeding behaviour and subsequently true breeding families were evaluated with check in M4. Most of the dwarfs were associated with pleiotropic effects pertaining to variable maturity, alteration in spike length and considerable changes in coleoptile length. The data which has emerged from different dwarf mutants of varied height have been summarised in Table 1. It was interesting to note that most of the dwarf mutants were recorded in EMS treatment (T14-EMS 0.1%). In the dwarf mutant lines, plant height ranged from 74 to 107, whereas in the control the height was 135 cms. In the mutant selection T14/P3-1, the two yield contributing traits-tiller number and spike length were enhanced. The positive change was reflected in the reduction in coleoptile and internode lengths. Relative performance of different dwarf mutants indicate considerable variability in height, tiller number, spike length, seeds per spike and single plant yield (Table 1). |
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