Heterotic performance of the main yield traits in different types of Indica hybrid rice

Abstract

Two-line hybrid rice with high efficiency and yield was successfully and widely being planted in China. HHZ is an elite inbred rice which is widely cultivated in Southern China. The latest developed engineered hybrid is promising for the future of hybrid rice breeding and production. In order to explore its heterosis performance, the main yield traits of two different groups of hybrid rice varieties and a inbred variety were investigated, specifically: (1) a large-scale extension of high-yield varieties of two-line hybrid rice and their parents (restorer lines), (2) a new generation of hybrid rice created by genetic engineered with HHZ as a background genome and its parental lines, and (3) a inbred indica rice variety, HHZ. We postulate that the performance of the main yield traits of genetically engineered hybrid rice may be better than that of commercial high-yielding hybrid rice in the same paddy field. To test our assumption, field experiments were conducted to investigate the performance of the main yield traits in the different types of hybrid rice and to compare and analyze the differences of the yield heterosis traits. The hybrid rice varieties showed obvious high-parent heterosis for effective panicle number (EPN) per hill, grain number per panicle (GNP), seed set rate (SSR), and harvest index (HI), but high-parent heterosis for the 1000-grain weight (KGW) was negative. Standard heterosis for GNP and KGW was found in the hybrid rice varieties, and the standard heterosis for EPN, SSR, and HI was negative. The grain number per panicle (GNP) is the largest contributor to heterotic performance. The genetically engineered hybrid rice showed similar heterotic performance to but not greater than that of two-line hybrid rice varieties. This study provides important insights for the breeding, cultivation, and popularization of different types of hybrid rice varieties.