GENE EFFECTS IN CORN (ZEA MAYSL.): I. SEPARATION AND RELATIVE IMPORTANCE OF GENE EFFECTS FOR YIELD

Abstract

A procedure is outlined for the separation, into six parameters, of gene effects affecting genetic variation of a quantitative trait. These parameters represent mean effects, additive and dominance gene effects, and the three types of digenic epistatic effects. Estimates of the parameters are obtained using the population means of two inbred lines, their cross, and descendants due to subsequent selfing and crossing. The relative importance of the different gene effects can be evaluated from the magnitude and significance of the estimates.Population means of six inbred lines of corn, and all possible F1, F2, P1F1, and P2F1 crosses among them, were used to obtain estimates of the various gene effects for yield of shelled corn. Mean yield performance of the populations was obtained from four experiments grown at two locations in each of 2 years.With regard to the 15 crosses, the estimates of gene effects indicate that the dominance gene effects were quite important in the inheritance of yield. Estimates of additive gene effects were of low magnitude and many were non-significant. Epistatic gene effects were considered to be more important than additive gene effects in the inheritance of yield in the crosses studied. The additive × additive and additive × dominance gene effects were relatively more important than the dominance × dominance effects.

Inheritance of resistance to Cotton leaf curl virus in cotton (Gossypium hirsutum L.)

“…Broad sense heritability was estimated as h = σ 2 F 2 -σ 2 D/σ 2 F 2 . Gene effect based on a six parameter model was estimated using the nonweighted method as described by Gamble (1962). The number of effective factors controlling resistance was estimated by five methods.…”

Genetic analysis of resistance to flower bud thrips (Megalurothrips sjostedti) in cowpea (Vigna unguiculata [L.] Walp.)

“…Generation means were calculated for each of the 6 generations on an individual plant basis. To determine the mode of inheritance of resistance to FTh, Gamble's (1962) notation was used, where m = F 2 mean, a = additive gene effects, d = dominance gene effects, aa = additive 9 additive epistatic gene effects, ad = additive 9 dominance epistatic gene effects and dd = dominance 9 dominance epistatic gene effects. The model for a generation mean, Y, is:…”

Genetic analysis of maturity and flowering characteristics in maize (Zea mays L.)

“…Generation mean analysis (GMA) is one of those biometrical techniques that involves estimation of the magnitude of various genetic effects (additive, dominance and epistatic effects). The estimates of genetic effects can help the plant breeders to decide the breeding procedures better suited for the improvement of trait(s) being analyzed [1] . Generation mean analysis, a biometrical method developed [2] , greatly helps in the estimation of various components of genetic variance.…”