Mapping QTLs For Heat Tolerance Of Seed Setting Rate And Heading Date By Using Chromosome Segment Substitution Lines In Rice

Rice (Oryza sativa L.) is one of the most critical cereal crops, providing necessary food for more than half people in the world. In China, about one third of the food crop seeded area is planted by rice. And rice is also the most important food crop. In recent decades, in order to meet the needs of the sustainable increasing population, continuous improvement of the rice quality and yieldis becomes a very important mission. But, the most of the yield-related traits were quantitative trait loci (QTLs), and as we all know, it is very difficult to map this QTLs by using traditional genetic materials and populations. Because of the simple genetic background, chromosome segment substitution lines (CSSLs) were generally considered as a kind of useful material to mapping complex QTLs.In our previous studies, we constructed a set of CSSLs, containing 163 lines, and the japonica Nipponbare and indica 9311 were used as recipient and donor, respectively. In present study, by using these CSSLs, we detected some QTLs that control the heat tolerance of rice seed seeting rate. Besides, we had finished a fine mapping and genetic analysis of a QTL (qHD8.2) which controls rice heading date. The main results are shown as followings.1. Shorten of the long substitution segments. In our research, we used a set of chromosome segment substitution lines.And at first, we shorten some of the long substitution lines.2. Mapping QTL for heat tolerance of seed setting rate.As the global temperature continuously raises up, high temperature stress has become one of the most important factors that affects rice yield. The high temperature during heading date would significantly affect rice seed setting rate and decrease the rice yield. Therefore, it is important to develop some rice with heat tolerant QTLs for guarantee the rice yield and reducing the effect of high temperature thermal pollution on rice yield. A set of rice CSSLs were planted at Yangzhou in the summer of 2012 and 2013. The temperature of 2012 summer is normal and the temperature of 2013 summer is higher. And then we divided D-value of two years’ seed setting rate by the seed setting rate of normal temperature year as Heat Tolerance Index (HTI). The software was used to conduct the preliminary gene mapping, total positioning three main effect QTLs related to rice heat tolerance, which distribute on the 2,4,12 chromosomes. One of them is a heat tolerance QTL, and the other two are heat labile QTLs. And this study provides materials which can support for follow-up fine mapping.3. Fine mapping and effect analysis of qHD8.2 for heading date. Heading date is one of the most important agronomic traits of rice, and it is also a typical quantitative trait. The heading date of the CSSL N22 line is earlier than its recurrent parent Nipponbare. The preliminary mapping results showed that N22 line carries a QTL qHD8.2 which is on chromosome 8. In this study, we carried out a further research on the QTL, and the gene location was further determined in a range of 460 Kb. Afterwards, we sequenced a candidate gene and compared to the results from other researches. We found that this candidate gene has a sequence mutation at coding region, resulting in lack of the function of this gene. Afterwards, we tested the relative expression level of this gene in the long day (LD) and short day (SD), these preliminary data help to understand the genetic mechanism and expression status of the qHD8.2.