Study On Mapping The Resistant Genes To The Whitebacked Planthopper, Sogatella Furcifera Using Rflp Markers

The whitebacked planthopper, So gate//a furcjfera, is one of the most important insect pests of rice. The genetic analysis of insect resistance in rice varieties using RFLP markers and mapping the resistant genes are very useful for breeding of rice varieties resistant to S. furcjfera. In present study, the resistant varieties ARC 10239 and Rathu Heenati (RHT), and susceptible varieties Minghui 63 and Taichung Native 1 (TN 1) were selected as parents to make crosses for F2 populations. Finally, the resistant gene Wbph2 have been mapped. 1. RESISTANT MECHANISMS IN THE PARENTS. Reaction of individual rice seedlings to S. furc/era at tillering stage indicated that RHT was immune to S. furcjfera, ARC 10239 highly resistant and Minghui 63 and TN1 susceptible. Honeydew measurement by S. furc~fera at seedling and tillering stages of these 4 varieties demonstrated that RHT and ARC 10239 possessed feeding inhibition property and none for Minghui 63 and TN 1. S. furc~fera excreted less honeydew at tillering stage than at seedling stage, especially on susceptible varieties. The nymph development postponed on RHT and ARC 10239 with the respective nymphal period of 1 8.6d and 1 7.9d whereas it was faster on Minghui 63 and TN1 with the respective nymphal period of 15.5d and15.5d. 2. GENETICAL ANALYSIS OF RESISTANT GENES IN THE TWO POPULATIONS. The F1 seedlings of ARC 1023 9/Minghui 63 and RHT/TN1 showed high resistance to S. furc~fera. The F2 populations segregated in a ratio of three resistant and one susceptible, demonstrating that the resistance in these two populations were governed by single dominant genes. 3. SCREENING FOR POSITIVE PROBES AND MAPPING THE GENE WBPH2. DNA from the susceptible F2 individuals in the populations of ARC 10239/Minghui 63 and RHT/TN1 were mixed respectively, forming susceptible bulks for screening positive probes. The DNA were digested with BarnH I, Dra I, EcoR V and Hind III and 129 probes screened, obtaining 6 and 5 positive probes, respectively. The polymorphism in ARC 10239/Minghui 63 and RHT/TN1 were 59.7% and 37.2%, respectively. Six positive probes in ARC 10239/Minghui 63 were used to screen for 142 individuals in the F2 populations, discovering that Wbph2 were co-segregated with the marker RZ667 on the chromosome 6 at the distance of 25.6 cM (LOD = 4.5) and 22.0% of recombinat ion value. Further screening of the adjacent probes indicated that RG64 and RG264 were also linked to Wbph2 with the distance of 27.8 cM (LOD = 4.32) and 36.4 cM (LOD = 2.56), and 25.2% and 3 1.1% of recombination value, respectively. Therefore, the gene Wbph2 has been mapped on rice chromosome 6.