To make efficient and effective use of mutant genotypes in advanced generations through selection, estimates of broad sense heritability and expected genetic advance with a selection intensity of five per cent have been computed for yield components.

The broad sense heritability (h) of a character was estimated (LARIK, 1978) as under :

%h= (sigma²g/sigma²t) x 100

where sigma²g=induced genetic variance and sigma²t is the total phenotypic variance calculated from mutant population.

The estimates of genetic advance (GA) at 5% selection intensity was based on the relation suggested by LARIK (1978) and computed by the following formula:

GA = (K)(sigmap)(H)

where sigmap=phenotypic standard deviation of the mean performance of mutant population, H=heritability coefficient and K=2.06 constant for selection differential.

Results and Discussion

Mean yield (g/plot) of mutant strains were compared by LSD method, which indicated that considerable genetic variability had been achieved through mutation (Table 1). The yield data reveal that most of mutant strains from C-591 and Indus-66 cultivars were low yielding compared with their respective controls. In Nayab both high and low yielding mutant strains were obtained. Similar results were obtained by GAUL (1965), SIDDIQUI and GHAFOOR (1974), LARIK (1975a, b). These authors also observed a decrease in the mean values and increase in genotypic variance in mutant populations concomitant with a high frequency of plants having values on the negative side of the control mean. In present studies two mutants (Nos. 44 and 27) derived from Nayab were the highest yielding among all mutants included in the experiment. Mutant-44 is significantly higher yielding compared with Nayab control when judged by LSD method. However, two mutant strains (Nos. 13 and 37) were significantly low yielding compared with Indus-66 control. Among C-591 mutants, although all strains were low yielding than C-591 control. but one strain (No. 28) was significantly different from the parent strain.

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 differences among strains and genetic variance indicates the potential for the improvement of a population. Keeping in view these points, the estimates such as genotypic co-efiicient of variation, heritability and genetic gain expected from selection were obtained separately from each quantitative character and are presented in Tables 2 and 3.