Abstract:

Further understanding the genetic regularity of rice harvest index in different segregating generations is beneficial to provide theoretical references for rice breeding based on the rice harvest index. In this research, isolated descendants from four distinct rice hybrid combinations were selected based on their harvest index. And then the coefficient of variation for main agronomic traits and the selection efficiency regarding the harvest index were subsequently compared and analyzed across different generations. The characteristics such as SPAD value at booting stage, plant height, and panicle length exhibited stability among different rice materials. In contrast, there was considerable variability in sword leaf length, thousand-grain weight, seed setting rate, and harvest index among hybrid rice progeny; however, these four traits remained stable in their parental lines. Notably, aboveground biological yield and panicle number per plant displayed significant variation both in hybrid parents and their offspring. The generalized heritability of the harvest index for F₃, F₃ lines and F₄ lines across all tested hybrid combinations exceeded 97%. Furthermore, selection efficiency for the harvest index in F₄ lines derived from ‘Hongxin-1S/Yuxiangyouzhan’, ‘Hongxin-1S/FL478’, and ‘Hongxin-1S/HD-YX’ surpassed that observed in their respective F₃ and F₃ lines; thus indicating a pronounced effect of single-plant selection based on harvest index within these three hybrids. Conversely, single-plant selection among offspring of ‘Hongxin-1S/Guanghong 3’ with high harvest indices did not enhance selection efficiency. It was effective to select individual plant with elevated harvest index for most of the tested rice materials from F₂ generation, which could significantly improve the selection efficiency of harvest index.

Key words: rice, conventional breeding, harvest index, agronomic traits, coefficient of variation, selection efficiency, hybrid combination, segregated generation