Factors affecting grain chalkiness in deepwater and floating rice (Oryza sativa L.)
1994
Charuwan Bangwaek
Chalkiness occurrence in deepwater and floating rice cultivars significantly varied at different locations indicating environmental influence. The occurrence of chalkiness followed the sequence of spikelet opening and filling in the panicle. The variation of chalkiness within the hill also depended upon the order of flowering. The panicles which flowered earlier had lower chalkiness. Results from scanning electron microscope indicated that chalky areas had loose compaction of starch granules which were of different sizes and round in shape compared to translucent grains which had compact granules of regular shape. Field experiment with different N rates applied at various stages of reproductive stage showed that increasing N at reproductive stage reduced the occurrence of chalkiness. On the other hand increasing P did not affect chalkiness when applied at reproductive stage, probably due to low efficiency of P absorption at this stage. The rates of water drainage during spikelet filling at HTA60 and PG56 showed no differences in chalkiness. However, complete drainage near harvest showed indications of lower chalkiness in HTA60. Improvement in grain quality through lower chalkiness is possible through better plant type such as lower number of spikelets on the secondary branches of the panicle and lower number of tillers per hill. Temperature regimes greatly affected chalkiness and development of cultivars less sensitive especially to high temperatures would greatly improve chalkiness. Cultivar differences in chalkiness is well known and the present experiment showed varietal differences in response to environmental factors. Thus, cultivars with inherently low chalkiness concomitant with greater adaptability to environmental factors affecting chalkiness is possible
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