Variations of Appearance Quality Among Grain Positions within Panicle in Japonica Rice.

Panicle is the key organ for yield formation in rice, and panicle type is an important component of plant type. The formation of panicle involves a series of physiological and biochemical processes, including the formation of inflorescence architectures, grain development etc. In this paper, the effect of panicle type on the grain weight and appearance quality among different grain positions within a panicle of japonica rice were studied using four types of panicles namely, Compact, Intermediate, Loose and Chicken toe; and 6 mutants for each type with contrasting grain number/panicle. There were significant differences in Secondary branches (SR) branches and the ratio of grain number (GN) and total branch length (TBL) among all panicle types. In general, Chicken toe panicle showed shortest panicle but substantially higher SR than others. Significant differences in grain weight and quality, including white-belly grain percentage (WBG), white-core grain percentage (WCG) and WCG/WBG were found among grains within a panicle, with the primary rachides (PR) branches having higher grain weight, WBG, WCG and WCG/WBG than the SR. Increasing the number of SR branches may reduce the variation in grain weight and quality within a panicle. Results suggest that panicle type should receive more attention in agronomical practices or in breeding selection aiming for reducing variations among grain position within rice panicle.

Keywords: Panicle types, grain position, mutant and japonica rice