Fine Mapping Of QBLSR5A,a QTL For Resistance To Bacterial Leaf Streak,Using Chromosome Segment Substitution Lines In Rice

Rice bacterial leaf streak is a common disease in the rice area of southern China,which has been one of the main diseases effecting the output and quality of the rice in China.Breeding new varieties which are resistant to the disease is an important task facing rice breeding.Therefore,deeply excavating the quantitative resistant loci(QRL)conferring resistance to rice bacterial leaf streak in germplasm resources of rice and clarifying the mechanism of the resistance has an important guiding role in breeding new resistant varieties.Based on the previous mapping,the fine mapping of qBLSR5A,which was located on the short arm of chromosome 5,was conducted in this study.The main results are as follows:1?Between SSR markers RM153 and RM413,12 SSR markers which can amplify clear bands and show polymorphism between H359 and H359-BLSR5A were obtained.The markers evenly covered a physical distance about 2296.Okb between RM153 and RM413.The average physical distance between two markers was only 208.7kb,of which the smallest distance was 52.7kb and the maximum distance was 324.7kb.2?Using 12 evenly distributed SSR markers,47 residual heterozygous between RM153 and RM413 were screened in F2 segregating population derived from the crossing between the H359 and H359-BLSR5A and self-crossing,then 12 homozygous chromosome segment substitution lines with different segments were screened in the offspring of the 47 residual heterozygous.Combining graphic genotype analysis with evaluation of disease resistance of the 12 segment substitution lines,the target QTL qBLSR5A was located between SSR markers RM153 and RM7029,the physical distance was about 400kb.3?On the basis of further mapping,the mixed offspring populations derived from residual heterozygous between RM153 and RM7029 were inoculated,237 extremely resistant plants and 205 extremely susceptible plant were selected.The extreme individual was tested using 5 markers such as RM153?RM5816?RM122?RM17750 and RM7029,12 homozygous segment substitution lines were obtined.Combined graphic genotype analysis with disease resistance of 14 segment substitution lines,the target QTL qBLSR5A was located between RM5816 and RM122 ultimately,the physical distance was only 52.7kb.