| Estimates of genetic variability in mutated population
of triticale M.M RAJPUR and A.J. MALIK Department of Plant Breeding and Genetics, Sind Agri. Univ. Tandojam, Pakistan. In various autogamous crops it has been now well established that radiations when applied to plants induce mutations in polygenic characters (GAUL 1977, LARIK 1978). Attempts have also been made to indentify and evaluate radiation induced variations in quantitative characters and have estimated the progress that can be made by subsequent selection. BROCK (1965) has put the hypothesis that random mutations are expected to increase the variance and shift the mean away from the direction of previous selection. Recently there has been a trend to apply mutation in already hybridized populations to find out whether or not variability could be extended. The present study was designed to compare the relative effiictiveness of X-rays and fast neutrons for inducing improvement in yield and yield components of triticale and wheat cultivars. Materials and Methods M3 populations of Norwegian highest yielding spring wheat variety "Runar" and Canadian spring form triticale derived from irradiation treatments of X-rays (3KR, 5KR, 10KR) and fast neutrons (1.5 N) were critically examined for spikes per plant, spikelets per spike, kernels per spike and seed set. Data on individual M3 plants randomly selected from each of M3 families were analysed. The heritability estimates was obtained from the following equation. Vt = Vg + Ve Where Vt stands for total variation, while Vg and Ve denoted components due to genetic and environmental variation respectively. Results and Discussion Response to selection for quantitative characters (i.e. yield components) is directly proportional to the function of its heritability and its genetic variance. Heritability enables a plant breeder to recognise the genetic difference among strains and variance indicatcs the potential for the improvement of a population. Keeping in view these points, the estimates such as genotypic coefficient of variatian and heritability were obtained separately from each quantitative character and are presented in Table 1. Productive tillers, florets per spike, kernels per spike and seed set are important yield components and are considered reliable measure of yielding ability (BOROJEVIC & BOROJEVIC 1972), as the frequency of induced changes in subsequent generation depends on the number of seeds which transmit them (LARIK 1978). Mean values for seeds per head and seed set characters (Table 1) were significantly (P>=0.05, 0.01) reduced in triticale after both the radiation sources, for florets and spikes (Table 1). The reduction was non-significant. Wheat displayed significant (P>=0.05) increase only for spikes per plant at 1.5 N and significant (P>=0.05, 0.01) decrease for seed set at 1.5 N and 5KR and for kernels per head at 1.5 N. The shift of mean values for these quantitative characters is mostly in negative direction in triticale and wheat gave plus as well as minus effects, it provides support for the hypothesis of GAUL & AASTVEIT (1966). |
| --> Next |