Quantitative inheritance studies in sugar-cane. III.* The effect of competition and violation of genetic assumptions on estimation of genetic variance components

Abstract

Several assumptions underlying the theory of quantitative genetics may not be valid for sugar-cane. The assumption of no epistasis was studied by comparing independent estimates of genetic variance components based on different genetic assumptions.

Sugar content was measured with excellent statistical precision, and independent estimates of genetic variance components for this character agreed very well, which indicated that violation of genetic assumptions had little effect on estimation. For other characters, agreement was not as good, and there was evidence to show that epistatic variance was important for weight per stalk. For all characters, maternal effects were negligible. Additive genetic variance was more important than dominance genetic variance for all characters except yield of cane, for which the two variances were equally important.

Inter-plot competition was unimportant, but several characters, notably yield of cane, exhibited substantial within-plot competition. This type of competition did not affect estimation of genetic variances, but has important implications for selection.

Estimates of heritability and degree of genetic determination were determined for each character studied.

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*Part II, Aust. J. Agric. Res., 22: 103-9 (1971).