| Carbon, nitrogen and prosperous metabolisms are most active during seed development in rice, which are closely related to the formation of yield and quality. In C metabolism, the assimilates transported from the leaves and stems are used for starch synthesis and deposited in the amyloplast of the starchy endosperm through carbon metabolism. The most nitrogen and phosphorus taken up from soil and stored in the shoots before flowering are assimilated, and accumulated in the form of protein and phytic acid. In a matured rice grain, carbohydrates, mainly starch is predominant, occupying about 90% of dry matter, followed by protein content, being about 8%, and phytic acid content is only around 0.8%. The bulk of proteins are deposited in protein bodies of the starchy endosperm, and phytic acid is also found in protein bodies, but it is mainly located in the aleurone layer and embryo. Chalkiness is the untranslucent part of rice grain, and was supposed to be the result of uncompleted accumulation of starch during grain development. Thus, chalkiness, phytic acid and protein content in rice grain is actually final demonstration of C, N, and P metabolism during grain development.The present research investigated the effect of genotype and grain position within a panicle on chalkiness, phytic acid and protein contents in japonica rice. Firstly, 72 cultivars from different locations of China were evaluated on chalkiness, phytic acid and protein contents, to determine the situation of rice quality in this area in terms of phytic acid and protein content, and the relationships among the three characters. Secondly, some genotypes with contrast performance in both phytic acid and protein contents would be used to study the effect of grain position on the three characters and determine their variation among grains within a panicle. The main results are shown as follows:1 The genotypic and environmental variation of grain phytic acid content in japonica ricePhytic acid and total phosphorus contents in grains of japonica rice cultivars, collected from different areas of China were assayed in this study. Meanwhile, a multi-location trial was conducted to determine phytic acid content of 24 cultivars grown at 4 locations with wide difference in ecological conditions. It was found that phytic acid content ranged from 0.685% for SH22 to 1.034% for Huai9746 among 72 genotypes, with a mean of 0.873%, and total phosphorus content ranged from 0.231% for SH22 to 0.388% for SH15, with a mean of 0.324%. There was highly significant correlation between grain phytic acid and total phosphorus content (r=0.7824**), indicating that total phosphorus, which is more easily measured, can be used as an alternative for phytic acid determination in low phytic acid rice breeding. The effects of cultivars, environments (locations) and their interactions on phytic acid content were all highly significant, with the location having the largest effect. The highly significant interaction between cultivars and environments suggests that the correct evaluation of rice germplasm in phytic acid content should be conducted under multi-environments.2 Genotypic differences in rice grain protein content and its relation to grain weight and phytic acid contentAveraged over 72 genotypes grown in Hangzhou, grain toatal protein, albumin, globulin, prolamin, and glutelin content were 8.72%, 0.352%, 0.352%, 1.021%, and 6.99%, respectively, with prolamin and glutelin having the least and largest CV, 7.89% and 15.07%, respectively. There were significantly positive correlation between albumin and globulin(r=0.4609**), and significantly negative correlation among grain weight and glutelin content(r=-0.2410*) and total protein content (r=-0.2480*). There was no significant correlation between grain phytic acid and protein content, suggesting the possibility to breed the japonica rice cultivars with low phytic acid and high protein content.3 Effect of genotype and grain position within a panicle on the occurrence of chalkinessAccording to the rati...
|
PDF Full Text Request