Genetic Relationships among and Selection for Rice Yield and Yield Components

Genetic correlations provide useful information to plant breeders for developing selection schemes. Genetic correlations among yield and yield components (panicle number, panicle weight, panicle length, primary branches, and plant height) for U.S. southern long‐grain rice ( Oryza sativa L.) have not been reported. The objectives of this work were to estimate and use genetic correlations in developing selection methodologies in rice breeding programs. In 1989, two 4 × 4 crossing factorials (Design II) were completed, and the 32 F 1 hybrids and the 16 parents were evaluated in 1990 at two Arkansas locations (Stuttgart and Marianna). Additive genetic and broad‐sense genetic correlations were estimated. At both the additive and broad‐sense genetic levels, yield was positively correlated with panicle weight. Yield was negatively correlated with panicle number, but the effect was diminished at the broad‐sense genetic level. Panicle weight was negatively correlated with panicle number. Path analysis, however, revealed positive direct effects for both panicle number and panicle weight on rice yield at both the additive genetic and broad‐sense genetic levels, with panicle weight exhibiting larger direct effects on yield than panicle number. Selection indices were developed from the additive genetic and phenotypic variances and covariances. The selection indices indicated that selecting for increased yield via selection for either panicle weight or panicle number alone would be ineffective. A selection index that included selection for both increased panicle weight and panicle number to increase yield was estimated to be 91% as effective as selecting for yield directly.