On biometrical genetics

Major Gene Locus of Spearman's General Factor of Intelligence

The reigning biometrical paradigm asserts that continuous variation implies the determination of intelligence by many genes with small effects. However, if an appreciable amount of the variability of a continuous trait is due to Mendelian segregation at a single locus, we may speak of the major locus for that trait. In such a case the distributions between the genotypic classes show considerable overlap, caused by error of measurement and environmental influences. As confirmed by Mendelian analysis, Spearman's general factor is the result of genotypes with discrete true scores of central processing time, the heterozygotes being exactly in the mean of the differences of the means of homozygotes.

Genotype x strain interactions for resistance to Fusarium head blight caused by Fusarium culmorum in winter wheat

In 3 consecutive years, a set of 17 winter wheat genotypes, representing a wide range of Fusarium head blight resistance, was inoculated with four strains of Fusarium culmorum. Fusarium head blight ratings were analyzed. The interaction between genotypes, strains, and years was described using a Finlay-Wilkinson model and an Additive Main effects and Multiplicative Interaction effects (AMMI) model. The interaction consisted primarily of a divergence of genotypical responses with increasing disease pressure, modified by genotype specific reactions in certain years. The divergence was mainly caused by one very pathogenic strain. The Fusarium head blight resistance in this study can be described as horizontal resistance in terms of Vanderplank, with the exception of three genotypes selected from one particular cross that showed a 'strain-year combination' dependent resistance which was ineffective in 1 year.

Combining ability and maternal effects in Brassica campestris L. var. 'yellow sarson'

A diallel analysis of combining ability, including maternal effects, genotype X environment interaction and the progress under selection, is reported in three selected crosses of Brassica campestris L. var. 'yellow sarson', involving 15 types, including 10 four-valved and 5 two-valved types from different parts of India. Twelve characters, including oil content, were studied in the f1 generation.The investigation has revealed only marginal superiority of f1's over the parents for most of the characters related to yield. There was no relation between heterozygosity and stability of performance over environments for yield or its components or for oil content. Substantial maternal effects were observed which also interacted with environments. Creation of variation for primary and secondary branches would be essential for changing yield level in 'yellow sarson'. The presence of limited additive variation available for selection for yield components should be augmented by biparental mating the early segregating generations to break linkages, and was demonstrated by the recombinants obtained when this method was adopted.The magnitude of genotype - environment interactions in this study, as compared with the total genetic components for yield, oil content, number of siliquae on main axis and presence of large reciprocal variances in relation to general and specific combining ability variances for practically all characters, and the large interaction of [Formula: see text], narrowed down the expected effectiveness of selection.Biparental mating in the three best crosses yielded three new recombinants outyielding the best check T 10 by the margins of 14%, 39% and 15%, respectively, in the yield trial. These recombinants had more primary branches and secondary branches, larger main axes and more siliquae with an increased number of seeds per siliqua, than any of the F1's in this study.