Fine Mapping Of Blast Resistance Gene PiLS(t) In Photo-thermo-sensitive Male Sterile Rice Line Long S

Rice blast is one of the most important diseases on yield and quality in rice production. It has demonstrated that development and utilization of disease-resistant varieties is the most efficient, economic and safest strategy, and identification, mapping and cloning resistance genes are the foundation of disease-resistance breeding. LongS, bred by Rice Research Institute of Hunan Agricultural University, is an elite photo-thermo-sensitive male sterile line and also shows a broad-spectrum resistance to rice blast fungus Manaporthe oryzae. To map and clone the blast R gene in LongS, Our previous results revealed that a dominant major blast R gene presented in LongS, designated PiLS(t), and this gene was mapped on the chromosome9. In this study, we performed a fine mapping of PiLS(t) gene by using the F2population from a cross by Long S and a susceptible cultivar Nipponbare(NPB). The main results are summarized as following:1. An F2population was constructed by the cross from LongS and a susceptible cultivar Nipponbare, and the rice blast isolate318-2from Hunan province was evaluated to be resistant to LongS, but susceptible to NPB, and was used for inoculation by F2population phenotyping.2. By inoculation of F2population with the isolate318-2. The results showed that in total of2393plants,1825plants were resistant, and568were susceptible. The segregation ration fits to3R:1S(resistant/susceptible), suggesting that a dominant R gene was presented. And the DNA of568susceptible individual plants was extracted for genotyping. The results showed that PiLS(t) gene was finely mapped between the markers RM7364and M2on the long arm of chromosome9, with a distance of0.23cM to RM7364, and1.26cM to M2, the physical distance between this two markers is110kb based on the reference genomic sequence of NPB.3. By comparing the reference genome sequence of NPB, PiLS(t) was located in three BACs, namely, OSJNBa0045M11, OSJNBb0051H02and OSJNBa0035G04.4. Two F2populations were constructed by the cross between LongS and two monogenic lines contained Pi5and Pii, two blast R genes located in the region close to PiLS(t), respectively. The two F2populations were inoculated with the isolate318-2, Thus, these results suggested PiLS(t) was not allelic with Pi5, Pii.5. By screening the BAC libaray of LongS using the linked markers RM7364and M2 closed the PiLS(t). One BAC clone21-1-3-9-1-8-5was screened that crosses the region between two linkage markes and is the candidate clones containg PiLS(t).