Analysis of embryo, endosperm, cytoplasmic and maternal effects for heterosis of protein and lysine content in indica hybrid rice

The heterosis controlled by genetic main effects and genotype × environment (GE) interaction effects for protein content and lysine content traits of indica hybrid rice, Oryza sativa L., was studied by using a genetic model for quantitative traits of triploid endosperm. The experiment was conducted over 2 years in a factorial design that included nine cytoplasmic male-sterile lines as females and five restorer lines as males. It was revealed that heterosis of protein content and lysine content were simultaneously controlled by genetic main effects and GE interaction effects. Maternal general heterosis and maternal interaction heterosis were observed. Embryo heterosis or cytoplasm heterosis for lysine content and endosperm heterosis for protein content were more important in general heterosis. Embryo interaction heterosis and cytoplasm interaction heterosis were more important for protein content, but endosperm heterosis was only important for lysine content in GE interaction heterosis. It was shown that some indica hybrid crosses had significant positive heterosis for protein content. Negative heterosis for lysine content was observed in most hybrid crosses.