| Brown planthopper (Nilaparvata lugens Stal., abbrievated as BPH) is one of the most serious pests of rice. Quality and quantitative resistance genes have been used in rice breeding. Many reports suggested that quantitative trait loci (QTL) are responsible for the durability of BPH resistance of rice. Development of molecular markers facilitates mapping of QTL. Mapping and cloning the BPH resistance QTL will be propitious to the development of resistant rice variety and understanding of BPH-resistance mechanism in rice.B5 and B14 derived their resistance for BPH from wild rices. Genetic analysis suggested the distribution of BPH resistant plants to BPH susceptible plants in the TN1/B5 F2 population is about 3: 1, while it is about normal distribution in TN1/B14 F2 population. Different interaction between two biotypes of BPH and the two rice lines were observed in the first 5 hours. There was little difference between the number of biotype 1 BPHs settled on B14 and susceptible check in free choice test. But much fewer BPHs settled on B5.A genetic map of rice covering 1,478 cM in the Kosambi function has been constructed using 187 F7 plants from a MH63/B5 RIL population. One hundred and fifty six RFLP markers from the Cornell University and Rice Genome Research Program (JRGP) and 53 SSR markers were located on the map using Mapmaker 3.0 with a LOD threshold 3.0. Except 3 gaps on chromosome 7 and 8, the markers distributed evenly on the map, and they are in good agreement with theorders in the published maps of the Cornell University and JRGP. It is providing a cross-reference to the two sets of high-density linkage maps, and suitable for QTL analysis.Dynamic analysis of QTLs for tillering ability based on the MH63/B5 RIL population was performed. Sequential records of tiller numbers of the RILs were analyzed by "Conditional mapping" approach, which was developed by Dr. Zhu for QTL detection of developmental trait, and traditional mapping. Three conditional QTLs and their net genetic effect were revealed. They showed higher statistic power than the QTLs detected in traditional mapping.The interaction between BPH and rice is a time depended trait too. Damage scores of the parents and RILs were evaluated every five days from 12th day after infestation by the insects. Six QTLs contributing to BPH resistance were detected and mapped by using either conditional or traditional mapping. Five BPH resistant QTLs are derived from B5, and one was derived from MH63. The contributions to BPH resistance of the QTLs displayed different dynamic curves, and most of them were active in early stage of BPH infestation, but the effect of BphlS lasted to the end of the test (27 days after BPH infestation). The results are valuable to development of resistant rice variety and understanding the genetics of BPH-resistance in rice.Dr. Wang and Yuan isolated Expressed Sequence Tags (ESTs) differentially regulated by BPH feeding by using techniques of the suppression subtractive hybridization (SSH) by. These ESTs were assigned to chromosomes based on RFLP mapping and rice genome database search. The distribution of the ESTs shows some level of clustering. Position coincidence of the ESTs and the BPH resistance genes/QTLs were observed. The feasibility of using differentially induced ESTs for candidate approach is discussed.
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