Inheritance Of Resistance To Sheath Blight In Rice (Oryza Sativa L) And Mapping Of Relative Major QTLs For Resistance

This study was conducted with a clonal F2 population of Teqing/Lemont. The F2 population, including 131 clonal families, was inoculated by short toothpicks incubated with a strain, RH-9 of the fungus. In 1999 each F2 clone was planted into one block with 8 plants for each line, while each was planted into two blocks in 2000. Based on field disease evaluations in two years and SSR(simple sequence repeats)markers distributed in rice genome, we constructed the genetic map combined with BSA(bulked segregation analysis) method. The main results are summarized as below:1) Polymorphisms between two parents: About 350 SSR markers were used to detect the polymorphism and 69 SSR primers showed polymorphism, The ratio of the polymorphism between two parents were 20%.(3%agrose) .2) Interval mapping analysis of resistance to rice sheath blight.In present study, we identified four major quantitative trait loci (QTLs) contributing to sheath blight resistance. These QTLs, qSB-7, qSB-9, qSB-11 and qSB-12, were located on Chromosome7, 9, 11 and 12, respectively. The respective alleles of qSB-7, qSB-9 and qSB-12 were from Teqing, while allele of qSB-11 was from Lemont. qSB-7 which could explain 28.7% or 25% of thetotal phenotypic variation, was located in the interval RM11-RM346 in two years. qSB-9 which could explain 16.4% or 24.1% of the total phenotypic variation, was located in the interval RM245-RM205, RM205-RM201, respectively, in two years. qSB-12 which could explain 20.9% of the total phenotypic variation, was located in the interval RM101-RM519 in one years. qSB-11 which could explain 20.4% or12.4% of the total phenotypic variation, was located in the interval RM167-IRM52 in two years.3) Interval mapping analysis of several agronomic characters.To understand the relationship between sheath blight and severalagronomic characters on the molecular level, In 1999, plant height and heading date were investigated. In 2000, productive panicle was also investigated. In the present study, we identified four major QTLs contributing to the agronomic characters. These QTLs. qE-2, qPH-2, qPH-3 and qHD-7, were located on Chromosome2, 3 and 7, respectively. qPH-3 which could explain 13.5% or 16.1% of the total phenotypic variation, was located in the same interval RM143-RM130 in two years. qHD-7 which could explain 15.8% or 17.9% of the total phenotypic variation, was located in the same interval RM214-RM2 in two years. In 2000, qE-2 and qPH-2 was located in the interval RM154-RM211, RM166-208, respectively. Two QTLS could explain 11.4% and 12.8% of the total phenotypic variation.From the results, we know, there is no linkage between QTLs contributing to the sheath blight and contributing to the agronomic characters.