Inheritance of high density grain in rice
1988
Mallik, S. | Aguilar, A.M. | Vergara, B.S. (International Rice Research Inst., Los Banos, Laguna (Philippines). Plant Physiology Dept.)
The parents, F1 and F2 of a cross of diverse parents IR30 and IR32385-37-3-3-3 (high density grain index [HDI] 56% and 29%, respectively) were grown in the greenhouse during 1987 wet season to study inheritance of this trait. HDI was calculated by dividing the number of high density grains specific gravity (Pb) and secondary (Sb) branches (50 panicles of each parent and the F1, 275 panicles of the F2). The F1 population with a wide range of variation (mean 76% Pb, 75% Sb), markedly exceeded the high parent (56%). The F2 population had a continuous distribution 10-90% Pb and 20- to 90% Sb, mean of 60% Pb and 59% Sb. The curve was unimodal, but skewed somewhat negatively. Only a few plants exceeded the lower parental limit and 20% exceeded the upper limit of IR30, indicating that multiple genes with opposite effects were operating. The dominance effect (Pb 34.0, Sb- 34.2) was 2-3 times higher than the additive effects (Pb- 16.4, Sb- 12.0). The potence ratio was more than 2 (Pb- 2.16, Sb- 2.60), indicating over-dominance of genes governing this trait. The effective factor pairs estimate was 0.5 for Pb and 1.26 for Sb, indicating that the trait is controlled by a few genes of the polymeric model. The degree of heterosis was 86.76 (Pb), 69.96 (Sb); heterobeltiosis was 33.22 (Pb) and 33.92 (Sb). The heritability estimate was very high, more than 80%. Thus, selections for more high density grain may be effective in early segregating generations such as F3 and F4. Forty F3 lines were selected to evaluate in the F4.
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