Fine Mapping And Candidate Gene Analysis Of QPSR8, A Major QTL For Pre-harvest Sprouting Resistance In Rice

Pre-harvest sprouting (PHS) before seed maturity or harvest,occurs frequently under a high temperature and long term of rainy weather, and is closely related to the yield and grain quality. In rice, more than100QTLs for seed dormancy and PHS were targeted by using different genetic populations,These QTLs are widely distributed on the12rice chromosomes.In Sichuan Academy of Agricultural Crops Research Institute, an F2population derived from G46B/K81was used to detect QTLs for PHS, and a major QTL named qPSR8was detected on long arm end of chromosome8. This QTL located in the DNA fragment between the SSR marker RM447and RM3754, and explained43.04%of phenotypic variation.The aim of this research is to fine map the major QTL, qPSR8and predict the candidate genes. The main results are as follows:(1) Based of the results in the previous study, those plants with high PHS resistance, from the BC3F2of G46B/Lemont were selected to backcross with the parent G46B.The closely linked SSR markers (RM447and RM3754) were used for detect target gene,qPSR8,and some other polymorphic markers for background selection.Subsequently, a near isogenic lines of G46B, named K7481,with single resistance QTL,qPSR8and good PHS resistance was obtained. Furthermore, the K7481was used to backcross with G46B,and an BC5F2groups was developed for fine mapping of the major QTL, qPSR8.(2) The PHS of the near-isogenic lines K7481, G46B, and5412BC5F2individuals were identified.The mean preharvest sprouting rate(PSR) of G46B was84.5%, while the K7481showed3.4%of PSR. And a total of1326plants with PSR of≥85%were selected as the extreme recessive single plants in this study.(3) The genomic DNA of those1326extreme recessive individuals were extracted and used for PCR analysis with the SSR markers RM447and RM3754, and76recombinants were screened and further used in the PCR analysis of the new SSR markers between RM447and RM3754, and the major QTL, qPSR8, was succesfully mapped on the103kb fragment between SSR markers RM23511and RM23520.(4) According to physical location of markers RM23511and RM23520,we analyse this section of the DNA sequence online by Based on available rice genome database website(http://rice.plantbiology.msu.edu/cgi-bin/gbrowse/rice/#search), there are12candidate genes in the region between SSR markers RM23511and RM23520, including two expressed protein genes, one hypothetical protein gene, one nodulin MtN3family protein gene,one zinc finger DHHC domain-containing protein geng, one mitochondrial import inner membrane translocase subunit Tim gene, one glycerophosphoryl diester phosphodiesterase family protein gene, one no apical meristem protein gene, one transketolase gene,one membrane associated DUF588domain containing protein gene, one CCT/B-box zinc finger protein gene and one annexin A7gene.