Mapping QTLs for Heat Tolerance in Rice (Oryza sativa L. ) at Heading Stage Using Chromosome Segment Substitution Lines

In the present study, a japonica rice （ Oryza sativa L. ） variety Nipponbare, an indica variety 9311 and a set of chromosome segment substitution lines （CSSLs） which were generated using Nipponbare as the recipient parent and 9311 as the donor parent were used as the experimental materials. The CSSLs were grown in 2012 （normal temperature condition） and 2013 （high temperature condition） in Yangzhou, Jiangsu, and were used to map the quantitative trait loci （QTLs） for heat tolerance, based on the heat tolerance index [ （The seed setting rate under normal temperature condition -The seed setting rate under high temper- ature condition） / The seed setting rate under normal temperature condition]. As a result, three QTLs related to heat tolerance in rice were mapped on chromo- somes 2, 4 and 12, respectively. They had LOD （logarithm of rntds） scores of 2.56, 4.02 and 2.79, and contributian rates of 4.95%, 7.99% and 5.44%. Among them, qHT12.1 showed positive effect, while qHT2.1 and qHT4. t showed negative effect on heat tolerance. The results lay a foundation for the fine mapping and cloning of the QTLs and genes related to heat tolerance, and for the breeding of heat-tolerant rice varieties.

Development and high-throughput genotyping of substitution lines carting the chromosome segments of indica 9311 in the background of japonica Nipponbare

Chromosome segment substitution lines（CSSLs） are useful for the precise mapping of quantitative trait loci（QTLs） and dissection of the genetic basis of complex traits.In this study,two whole-genome sequenced rice cultivars,the japonica Nipponbare and indica 9311 were used as recipient and donor,respectively.A population with 57 CSSLs was developed after crossing and back-crossing assisted by molecular markers, and genotypes were identified using a high-throughput resequencing strategy.Detailed graphical genotypes of 38 lines were constructed based on resequencing data.These CSSLs had a total of 95 substituted segments derived from indica 9311,with an average of about 2.5 segments per CSSL and eight segments per chromosome,and covered about 87.4%of the rice whole genome.A multiple linear regression QTL analysis mapped four QTLs for 1000-grain weight.The largest-effect QTL was located in a region on chromosome 5 that contained a cloned major QTL GW5/qSW5 for grain size in rice.These CSSLs with a background of Nipponbare may provide powerful tools for future whole-genome