Mapping Blast Resistance Gene Of Photo-thermo-sensitive Male Sterile Rice LongS

Rice blast is one of the three major diseases in rice production worldwide, which is responsible for serious losses every year. It has proved that, utilizing varieties with blast resistance is one of the most effective way to reduce the loss.This study aims to map the blast resistance gene in Longs and results are as follows:(1)Analysis the resistance spectrum of LongS using indoor inoculation method. The result showed that LongS was highly resistant to 33 strains of rice blast including IC-17, P06-6,which come from Philippines, and 110-2,236-2,193-1-1,195-2-2,236-1,87-4,318-2 which come from blast-prone areas of Hunan Province. LongS, as an elite photo-thermo-sensitive male sterile line, is of great value in practical use.(2) 848 SSR markers on 12 chrosomes of rice were used in this study.It showed that the polymorphism rate were 16.75% between Longs and CO39 and 33.84% between LongS and Nipponbare. It was proved that the polymorphism detection rate between Indica varieties was significantly lower than Japonica-Indica varieties.We had constructed an SSR marker lingkage map between LongS and CO39 which contains 142 markers. There are 11 breaking points(three on each chromosome 2,3 and one on each chromosome 1,4,5,6,9) on the map due to markers on the map are not evenly distributed, the largest blank area upto 47.5CM is in chromosome 2. There are 3 breaking points on the lingkage map of LongS and Nipponbare, two in chromosome 2 and one in chromosome 4.(3) LongS and Nipponbare were used as the parental lines for the construction of the F2 mapping population.Inoculating the population with a rice blast isolate 318-2 and the result indicated that blast resistance gene to 318-2 of LongS is controlled by single dominant gene. To rapidly determine the chromosomal location of the major resistance gene present in the cultivar, a linkage analysis using SSR markers was performed in the F2 population. A total of 290 SSR markers selected from each chromosome equally were tested with the bulked-segregant assay approach. Only three markers, RM7212, RM3912 and SFP-9-2, located on the long arm of chromosome 9 showed positive and negative polymorphisms, respectively, for a resistance gene segregating in the population. To confirm the polymorphic markers, a total of 34 viable susceptible individuals were tested with the recessive class analysis approach. The markers RM7212, RM3912 and SFP-9-2 were found to link to the resistance gene with recombination rates of 13.24%,7.35% and 2.94%.