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Additive (D), dominance (H) and environmental (E) components of variation and narrow sense heritability estimates of various quantitative traits for cross PARI-73 x V-7682 wheat genotypes.
In this study, narrow sense heritability for RSG and RGR groups of lines was 24.90 and 21.21 per cent respectively.
The broad and narrow sense heritability was 97.5% depicting that the character is highly heritable in this irrigation treatment and quite a significant amount of improvement is expected to be brought about while selecting the genotypes/hybrid combinations under high selection pressure from the progeny rows.
Estimates of broad sense and narrow sense heritability were calculated for seed Zn concentration by using the variance of the parent, [F.sub.1][F.sub.2], and backcross generations to estimate phenotypic ([V.sub.P]), environmental ([V.sub.E]), total genetic ([V.sub.G]), additive genetic ([V.sub.A]), and dominance genetic variances ([V.sub.D]).
The significant realized heritability estimates were in close agreement with the (mostly) nonsignificant estimates of narrow sense heritability from the sib-analysis (Table 3).
Narrow sense heritability assesses the extent of additive genotypic variation which is primarily responsible for modifying the genetic makeup of a population.
To ascertain expected genetic gain per selection cycle, we calculated narrow sense heritability estimates.
The narrow sense heritability of corolla length in an annual Phlox was 0.14 (Schwaegerle and Levin 1991), lower than the estimates obtained here from half-sib analysis ([h.sup.2] [is greater than or equal to] 0.24-0.67).
Narrow sense heritability (h2ns) was also calculated using the components of variance from the best-fit model of weighted least squares analysis (Mather and Jinks, 1982).
Abbreviations: [H.sub.ns] = narrow sense heritability; RIL, recombinant inbred line.
Population density can greatly affect the response to selection (Charlesworth, 1971; Mueller et al., 1991), which is the product of narrow sense heritability ([h.sup.2]) times selection differential (Maynard Smith, 1989).
In crop plants, generally, heritability estimates in broad sense are higher than narrow sense because narrow sense heritability uses only additive genetic variance as a numerator over the total phenotypic variance.