Primary Quantitative Trait Loci Mapping Of Unstripped Germ Rate And Corelation Between Unstripped Germ Rate And Grain Character In Milled Rice

As the population’s standard of living improves, people pay more attention on the nutrition of food, which makes functional rice a hot topic. Rice germ contains rich protein, fat, vitamins and trace elements, however, it almost loses during milling period, which makes rice varieties with high unstripped germ rate a new research direction. Z601(a variety with high unstripped germ rate)、C14 (a variety with low unstripped germ rate) and recombinant inbred lines which were constructed by the cross between them were used to optimize the germination condition by response surface methodology, identify quantitative trait loci (QTLs) controlling unstripped germ rate and discuss the correlation between unstripped germ rate and grain characteristics. The major results were as follows:(1) Germ-remaining rice Z601 was used as material to accumulate GAB A content during germination. A quadratic polynomial model was established for GABA content as a function of four variables which were soaking temperature and time as well as germination temperature and time. The optimum conditions were as follows:soaking temperature at 31℃, soaking time at 13h, germination temperature at 31℃, germination time at 27h. Under the optimum condition, GABA content reached 31.13mg/100g, which was almost 4 times higher than that in the rice which did not germinate.(2) A whole genome linkage genetic map containing 70 markers was constructed by QTL IciMapping V3.0, with total length of 1889.15cM on whole 12 genomes. The average distance between makers 27.00cM. Eight QTLs (qUGR-3a、qUGR-4a、qUGR-6a、 qUGR-7a、qUGR-8a、qUGR-8b、qUGR-9a、 qUGR-12a)distributing on the seven chromosomes were detected on chromosome3,4,6,7,8,9 and 12, respectively. Among them qUGR-8a and qUGR-8b were most valuable for fine mapping, gene cloning whose LOD score were 17.38 and 17.90 explaining the phenotypic variation of 43.52% and 39.86%, respectively.(3) Unstripped germ rate in milled rice had a significant positive correlation with the circular degree, and an a significant negative correlation with grain length width rate. It also had a negative correlation with the circumference and grain length, and positive correlation with the width. The result shows that reducing length width rate and increase the circular degree can make unstripped germ rate high.The results and the tightly linked molecular markers that flank the QTL will be useful in breeding for improvement of unstripped germ rate in rice and comprehensive utilization of milled rice.