Abstract:

Improvement of harvest index (HI) has become one of the main objectives in rice breeding. It is very important to know the genetic regularity of rice HI for yield improvement. The experiment was conducted with complete diallel crossing design, using 5 rice cultivars with different characteristics. The results indicated that general combining ability (GCA), special combining ability (SCA) and reverse crossing effect of the HI were significant at 0.01 probability level, and their variance ratio was 2.595∶1.232∶1；HI from low to high in F₂ populations was distributed serially and normally, showing the heredity of quantitative character；additive effect and dominance effect were significant at 0.01 probability level in additive-dominance model；Narrow-sense heritability and broad-sense heritability were 40.17% and 67.94%, respectively. The genetic correlation analysis showed that HI was significantly correlated positively with grain filling rate, and negatively with ear length, 1000-grain weight, and biomass. The improvement of HI would be effective by selecting ear length and 1000-grain weight during early generation, which had higher heritability. It was preliminarily revealed that: rice HI is a quantitative character and fit into additive-dominance model with mainly additive effects, simultaneously dominant effect and somewhat other effects (e.g. reverse crossing effect). HI has a higher heritability and can be selected in early segregating generation, which is useful for rice breeding.

Key words: Rice (Oryza sativa L.), Harvest index, Heredity, Agronomic character