Fine Mapping Of QSB-9^TQ, A Quantitative Trait Gene, Controlling Resistance To Rice Sheath Blight

Sheath blight is one of the three most serious diseases in rice worldwide. The resistance to this disease is a typical quantitative trait. Up to now, there were some resistance QTLs mapped on all12rice chromosomes, of which, the frequence detected resistance QTLs on Chromosome9was the highest.We identified a quantitative trait locus (QTL), qSB-9, from Teqing using a set of F2clonal population from a cross TQ/LMNT, which, by constructing and investigating disease rangting of NILs, has been confirmed between the markers of Y242and Y93.5. Then, the strategy of constructing chromosome single substitution segment lines (CSSLs) was adopted to carried out fine mapping of the QTL.Meanwhile, another quantitative gene, qSB-9TAC controlling the tiller angle of rice, was also detecting in the same interval. This study also analyzed its effect on alleviating sheath blight disease and interactive effect with qSB-9. The results suggesteded that qSB-9TAC and qSB-9TTQ not the same gene. But qSB-9TAC has indirect impact to rice sheath blight resistance and week associate effect with qSB-9T-. The existence of qSB-9TAC partly impacted the fine mapping of qSB-9TQ.We develop a set of chrmosome single segment substitution lines (CSSSLs) covering the target interval and difine the qSB-9interval in between Y82.1and Y93.5on the right side of qSB-9TAC. Further CSSSLs coverd sub-interval and without tiller angle gene was developed through the development of polymorphism markers. Eighty three CSSSLs, involving16substitution genetypes, were selected for inoculation experiment on paddy in2010and2011.According to the average disease rating and/or disease index of the different substitution genotypes or all CSSSLs, clustering analyses were conducted to distinguish relative resistant from susceptible types or lines and to fine map qSB-9TQ. The results suggested that qSB-9T-was in the maker interval between Y84and Y86with about293.5kb of physical distance.We further developed CAPS makers to narrow the interval of qSB-9TQ botween GZ12and Y86. The physical distance is about146kb. Therefore we achieve the goal of the QTL of fine mapping. Moreover, we discovered a resistant QTL, qSB-11LMNT, on the chromosome11during the process of fine mapping of qSB-9T-. This study analyzed their alone effects and polymeric effect. The results revealed that qSB-11LMNT and qSB-9TQ have significantly resistance effect to sheath blight of rice. Both of the QTLs reduced sheath blight disease clearly about1.0score and significantly improved the resistance of rice sheath blight. However, polymeric effect was not so significantly.