Heat Tolerant Evaluation And QTL Mapping Under Flowering Stage In Indica Rice

In this study, Shuhui527, a widely used indica restorer, was used as recurrent parent, six indica varieties (Minghui63, Fuhui838, Gui99, PU28, IR64 and Zihui100) with distinct genetic diversities as donors for developing six BC2F4 backcrossing populations, from which 26,19,20,21,21 and 24 introgression lines (ILs) were selected. The progeny of the BC2F3:4 populations and their parents were tested for heat tolerance (HT) in consecutive two years (2011 and 2012) in Changsha, Hunan. Phenotyping and genotyping for these populations were conducted for QTL identification of yield related traits and heat tolerance. The main results are as follows:1. The high temperature stress had large impact on panicle per plant, filled grain rate per panicle, grain yield per plant and the heat stress index, followed by filled grain number per panicle and spikelet number per panicle while high temperature stress had weak impact on plant height, heading and thousand grain weight.2.Correlation analysis showed that heat stress index was significantly or very significantly negative correlated with filled grain per panicle, spikelet fertility and grain yield per plant. The heat stress index was mainly determined by spikelet fertility and correlated with other yield components.Therefore, it is necessary to pay particular attention to spikelet fertility, filled grain per panicle and grain yield per plant of varieties in the practice breeding, and the relationship among yield components should be considered.3. QTL mapping results showed that 86 QTLs related to yield traits and heat resistance (heat stress index) were detected in six populations, including 78 QTL related to yield, the contribution rate of these QTLs was ranging from15.9% to 67.4%; 21 heat resistance QTLs, the contribution rate was ranging from 16.2% to 57.4%. Among them,31, 34,20,29,22,14,42 and 19 detected QTL were controlling heading date, plant height, panicles per plant, filled grain number per panicle, spikelet number per panicle, filled grain rate per panicle, thousand grain weight and grain yield per plant.4. In Shuhui 527/PU28 population we detected a locus (qTGW3a) that control grain weight and closely linked with RM007,and this locus were both detected in two environments in 2011 and 2012, their additive effect is positive.This shows that the allele from donor parent PU28 has a posotive effect for increasing thousand grain weight and has a higher contribution rate.This locus maybe can express steadily and it’s inferred taht it may be a major gene controlling thousand grain weight.All the qTGW1b、qPN2b、qPN9a in Shuhui527/Gui99 population and qPN2a、qTGW3d in Shuhui527/Zihui100 populaion were detected in two environments of 2011 and normal environmental condition of 2012,and among them,the additive effect of qPN2a、qPN2b and qPN9a are positive,while the additive effect of qTGW1b and qTGW3d are negative,and all of them are locuses that can express steadily.5. The identified QTLs were mostly clustered distribution; each cluster often affects several traits.58 QTL clusters were detected in six populations, i.e RM297 near QTL cluster on chromosome 1, controlling plant height, heading date and thousand grain weight; RM290 near QTL clusters on chromosome 2 controlling heading date, plant height, panicle number per plant, filled grain number per panicle, filled grain rate per panicle, thousand grain weight and grain yield per plant; RM007 near QTL cluster on chromosome 3, was mainly related to plant height, filled grain number per panicle, filled grain rate per panicle, thousand grain weight and grain yield per plant. In addition, RM186 and RM520 on chromosome 3, RM1155 on chromosome 4, RM153 on chromosome 5. It was noteworthy that RM007 near QTL clusters on chromosome 3 which related to thousand grain weight had been detected both in 2011 and 2012 in Shuhui527/PU28 population with positively additive effect, indicating the donor parent PU28 allele increased thousand grain weight, and possessed a higher contribution rate. Thus, it might be a stable expression QTL, which may infer a main-effect gene controlling thousand grain weight.