Positional variations in chalky occurrence within a rice panicle and its relation to grain nutritional quality

The effect of grain position within a panicle on chalky occurrence, and its relation to phytic acid and protein content, were studied using 6 Japonica rice cultivars with compact panicles and through leaf and floret removal treatments to alter source-sink ratio. There were significant differences in total chalky grain (TCG), white core grain (WCG), white belly grain (WBG), and WCG/WBG among grains within a panicle, with the top and primary rachides having higher WBG than the bottom and secondary rachides. Alteration of source-sink ratio had a remarkable influence on chalky grain occurrence and its positional distribution within a panicle, and the extent of the influence varied greatly with cultivars. In comparison with WCG, WBG occurrence was more susceptible to the alteration of source-sink ratio. No significant correlation was found between chalky percentage and phytic acid and protein contents for the grains in the different positions within a panicle. Chalky occurrence had little effect on the nutritional quality.