Effects Of High Temperature On Rice Chalky Formation And Heat-tolerance QTL Analysis Of Chalkiness

Taking two rice lines including heat-tolerance line 996 and heat-sensitive line 4628 as materials, the trials were conducted in growth chamber to investigate the effects of high temperature and optimal temperature on grain accumulation,starch structure,starch synthesis enzyme activity and endogenous hormones in endosperm..In addition, the preliminary QTL mapping of chalkiness in rice under high temperature stress were carried out with RILs derived from 996 and 4628 as the materials,which used the chalky rate heat tolerance index,chalky area heat tolerance index and chalky degree heat tolerance index as the evaluation indexes. The results are as follows:1. The high temperature stress resulted in the increase of grain dry 1000 grains weight during grain filling stage. With the stress time prolonged, it also decreased the grain dry matter, broke grain filling down and decreased some contents which were the grain weight starch content, soluble sugar content. Sucrose content and protein content in grain were raised under high temperature stress during the filling stage,t decreased with stress time extended.Under high temperature stress,starch granule arranged untightly,most of starch granule existed in the form of a single starch endosperm, refractive index decreased, transparency reduced,and led to the formation of chalk.2. The AGPase, SSS and SBE enzyme activities increased under high temperature stress, then decreased after the period of the peak.the decreasing extent in heat resistant line 996 was lower than that in heat sensitive line 4628.There was a significant correlation between the starch accumulation rate and the AGPase?SSS activities.3. The ABA content increased, IAA content and Z+ZR content decreased under high temperature stress, the change scope of endogenous hormone content in heat-tolerant line 996 was greater than that of heat sensitive line 4628.4.24 QTL associated with chalky stressed with high temperature were detected on chromosome.8 QTL associated with chalky rate were detected on on chromosome 1,3,6,7.12 QTL associated with chalky area were detected on chromosome 1,2,4,6,7,10.4 QTL associated with chalky degree were detected on chromosome 1,3,7. The 2 QTL of chalky rate were detected in 2014 and 2015.The qCR6.1 was located in the interval flanked by the markers RM3353 and RM1369, with a LOD score of 4.44,7.24 and with contribution rate 14.24% and 12.14% in 2014 and 2015, respectively. The qCR6.2 was located in the interval flanked by the markers RM1369 and RM190, with a LOD score of 4.78,4.74 and with contribution rate 17.89% and 14.25% in 2014 and 2015, respectively. The 2 QTL of chalky degree were detected in 2014 and 2015.The qCA7.1 was located in the interval flanked by the markers RM21327 and RM21364, with a LOD score of 4.68,5.54 and with contribution rate 13.27% and 17.44% in 2014 and 2015, respectively. The qCA7.2 was located in the interval flanked by the markers RM21364 and RM3859 with a LOD score of 4.25,6.25 and with contribution rate16.32% and 29.52% in 2014 and 2015,respectively.