| Magnitude of change induced through X-rays and fast
neutrons in Triticale* M.M. RAJPUR and K. AASTVEIT Plant Breeding and Genetics, Sind Agriculture University, Tandojam, Pakistan. and Plant Breeding and Genetics, Agricultural University of Norway. Most important cereal crops used as food or feeding stuffs, were domesticated thousands of years ago and all have been improved by human beings from time to time. Yet these improvements were not enough to fulfil the needs of increasing population of the world. Therefore the search for high yielding varieties and new crops remained open for the research workers. Very recently an entirely new cereal grain crop-Triticale-has been produced, which appears to have the potential of producing more yield per unit area than all of the existing traditional cereals (MUNTZING 1979). However, the triticales now available have a narrow genetic base, because they were derived from a limited number of primary triticales (KALTSIKES 1974). Enlargment of this genetic variability is obviously needed, so that suitable plant types of this crop may be developed. It has been reported that different types of mutagens could be used to induce variability in quantitative characters in different crop plants (AARTVEIT 1968). Such attempts have also been made on triticales. VETTEL (1960) and RAMANATHA & JOSHI (1976) found that a greater variability could be produced through induced mutations in triticale rather than by hybridization technique. The present study was also designed to discuss the nature of quantitatively induced variations with a special reference to the genetic improvement of triticale mediated through the yield and various yield components. Materials and Methods Seed of a Canadian Triticale Spring Farm were subjected to different mutagenic treatments of X-rays (3 kR and 5 kR) and fast neutrons (1.5 N). At maturity the earheads were harvested from each treatment. These treated seeds were grown to obtain the M2 population with untreated seeds as control. Thirty plants were selected at random from each of the treatment. Observations were recorded for straw length, number of spikes per plant, number of florets per spike, number of kernels per spike and spike fertility. Variances (Var), genetic variance (Vg) and broad sence heritability h2(bs) were calculated. Results and Discussion The data regarding means, ranges, variances, coefficient of variation and heritability for all the characters studied in the M2 generation of triticale are given in Table 1. Straw length being controlled by polygenes has an evalutionary significance (LARIK 1978). It is associated with the efficient utilization of nitrogen, lodging resistances and thus influence the crop yield (JOPPA 1973). The results obtained in respect to straw length (Table 1) reveal that the mean values decreased significantly (p = 0.01) in response to the increased radiation doze in all the treatments as compared with control. These results are similar to those reported on wheat by various workers. For example, Gaul & AASTVEIT (1966) and BOROJEVIC & BOROJEVIC (1972) found that irradiation treatment resulted in the dwarfness of wheat plants. In particular, the dwarfness was more pronounced among the material treated with higher radiation doses. Furthermore, the occurrence of mutants with short culm, often accompanied by straw stiffness in irradiated wheat and barley has also been reported (BROCK 1967 ; SIDDIQUI 1972). Segregate in downward direction observed in the present triticale might be useful in producing high yielding dwarf types. Heritability estimates regarding straw length (Table 1), show a highly significant increase in the genetic variation in treated population of triticale. The large variabilities observed in the present study may possibly offer better scope of selection in the further segregating generations. |
| * Present studies is part of the Ph. D. thesis presented in the Agricultural University of Norway. |
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