Estimation of genetic parameters for in vitro traits in wheat immature embryo cultures involving high X low regeneration capacity genotypes

Abstract

Estimates of gene actions were obtained for five in vitro traits of immature wheat (Triticum aestivum L.) embryo cultures from a cross of two wheat cultivars and the resulting reciprocal, Fl, F2 and backcross populations. The contribution of additive gene effects to in vitro traits was not as important as the dominance gene effects. Epistatic gene effects were relatively more important than either additive or dominance gene effects. Of the individual types of digenic epistatic effects, the dominance x dominance estimates were relatively larger in magnitude for all in vitro culture traits measured. The maternal effect played a minor role in the inheritance of the in vitro studied traits since the difference among the reciprocal values was not significant. It is shown from the generation mean method that epistasis played a major role in the inheritance of most of the traits under study, The negative values of additive and dominance genetic variance were estimates of zero. Heritability estimates, in broad sense, were relatively high for the in vitro studied traits. In some cases, heritability estimates in broad and narrow senses are almost equal since the estimation of dominance genetic variance led to negative values. According to the results of the gene effects, dominance and epistasis were important for the shoot formation trait. Selection would be effective among the isolated genotypes on individual basis.

Genetic control and transgressive segregation of zinc, iron, potassium, phosphorus, calcium, and sodium accumulation in cowpea (Vigna unguiculata) seeds

“…As expected, all the variances were positive with the exception of dominance variances, which showed negative values in close proximity to zero (Table 2). Negative variances have been reported by Barakat (1996) for wheat and by Hallauer et al (2010) for maize. When negative dominance variance values are observed they are assumed to be equal to zero (Barakat, 1996), transforming the broad-and narrow-sense heritability values into the same value for all mineral contents.…”

Genetic Analysis of Total Seed Protein Content in Two Cowpea Crosses

“…The only exception was the dominance variances that presented close to zero or negative values. Negative dominance variances have also been reported in wheat ( Triticum aestivum L.) (Barakat, 1996) and in maize ( Zea mays L.) (Hallauer et al , 2010). Under these special circumstances (negative dominance values either equal or close to zero) the narrow‐ and broad‐sense heritabilities will assume identical values (Barakat, 1996).…”

Components of variation of polygenic systems with digenic epistasis

“…or triple test cross analysis (Ramsay et al, 1994), or with analysis of variation without epistasis (Holtom et al, 1995;Barakat, 1996). A limitation of generation mean analysis is that the absence of the linear components attributable to epistatic effects does not imply the absence of epistasis, since the linear components of means can be null even when constituent effects are not.…”

“…In genetic studies it is commonly thought that epistatic effects contribute little to the genotypic values of individuals, and that epistatic variance is small or negligible compared to both additive and dominance variance. However, there is evidence from many analyses that epistatic effects cannot always be ignored (Rishipal, 1993;Ramsay et al, 1994;Saha Ray et al, 1994;Rahman et al, 1994;Mgonja et al, 1994;Bartual et al, 1994;Das and Griffey, 1995;Barakat, 1996).…”