Quantitative Trait Loci Controlling Sheath Blight Resistance In Two Rice Varieties

This study was conducted with a clonal F2 population from the cross between Lemont and Teqing .In 1999 each F2 population was planted into one block with 8 plants for each line while each were planted into two blocks in 2000.The population which includes 143 clonal families were inoculated with RH-9 fungus.The extreme lines were selected to construct resistance and susceptibility DNA pools, respectively, for bulked segregant analysis.The main results are summarized as below. 1. There were abundant polymorphisms between two parents. 28 RFLP probes and 320 microsatellite primes were used to detect polymorphism, 21 RFLP probes and 220 microsatellite primes showed polymorphism, the ratio of polymorphism between two parents was 69%. The result indicated that this cross was an ideal research material for genetic map construction and gene mapping. 2.lnterval QTLs analysis of resistance to rice sheath blight: In the present study, two major QTLs for rice sheath blight were identified in both years. The probes which revealed polymorphism between two parents were chosen for further analysis between two DNA pools, and five primers were discovered, three of them on chr 9 and the other two on chr 11 .The two QTLs were named qSB-9 and qSB-1 I respectively. qSB-9 was located in the interval between RM2OS-RM2Olin both two years .And qSB- 11 was located between RM 167 and RM2OB in 1999 and RM202 and RM167 in 2000,but both near to RM167,the middle primer .qSB-9 could explain 12.9% and 15.3% of phenotypic variation respectively and qSB-llcould explain 20.7% and 11.6% of phenotypic variation respectively 3.Interval QTLs analysis of some morphological characters: With the constructed map some other QTLs were located with SSR .4 primers. One QTL (qPH-12) controlling plant height was discovered in 1999, one QTL (qEH-2) controlling effective panicle in 2000, and the other QTL (qHD-7) controlling heading date was discovered in both two years. These QTLs could explain 10.5%, 7% and 11.5% of phenotypic variation, respectively.