DIFFERENCES IN PROTEIN-CONTENT, AMYLOSE CONTENT AND PALATABILITY IN RELATION TO LOCATION OF GRAINS WITHIN RICE PANICLE

The protein and amylose content of milled rice grains collected from t he top and base rachis branches at different positions on the panicle were measured. The palatability of the grains on primary and secondary rachis branches were also investigated. Grains on upper rachis branch es had a lower protein content than those on lower rachis branches wit h a gradual change from the base to the top of both primary and second ary rachis branches. Grains on primary rachis branches also had lower protein content than those on secondary rachis branches at any positio n within the panicle. Conversely, amylose content on upper rachis bran ches was higher than that on lower rachis branches, and that on primar y rachis branches was higher than that on secondary rachis branches. P rotein content and amylose content varied widely within the panicle wi th 1.2% and 3.3%, respectively, range at maximum. Grain weight was neg atively correlated with protein content and positively correlated with amylose content. Grains which originated from early flowering spikele ts generally had low protein content and high amylose content. The pal atability of the grains on primary rachis branches was superior to gra ins on secondary rachis branches, both in Koshihikari and Nipponbare. It was concluded that the variations in protein content and amylose co ntent, and differences in palatability within a rice panicle were caus ed by the differences in the extent of grain filling, which was closel y related to the flowering order of spikelets. This leads us to suppos e the varieties with high and stable palatability in any growth enviro nment could be raised from genetic resources which have more grains on primary rachis branches in the ear or on the secondry rachis branches in the upper position of the ear.