| The whitebacked planthopper (WBPH), Sogatella furcifera Horváth and brownplanthopper (BPH), Nilaparvata lugens St?l, are important sucking insect pests of rice(Oryza sativa L.) throughout the world. Recently, the study and utilization of resistant ricevarieties are getting more and more important in the integrated management of riceplanthoppers. However, the changes in insect biotypes and disease races are a continuedthreat to increase rice production. There is thus an urgent need to identify and introducenew genes for resistance to diseases and insects into rice varieties from diverse sources.Wild rice is an important reservoir of such genes. Wild relatives of cultivated rice remain to be highly diversified and hold variousgenes conferring resistance to biotic and abiotic stresses, thus providing a valuable genepool for rice genetic improvement. More and more attentions are paid to introgression ofbeneficial alleles from wild rice into elite breeding lines. To provide a tool for evaluationand utilization of the potential of O.rufipogon in rice breeding, we developed aninterspecific genetic linkage map consist of 45 RFLP markers and 82 SSR markers derivedfrom a set of backcrossing inbred line (BIL) population cosistant of 202 individuals(XieqingzaoB//XieqingzaoB/Dongxiang wild rice) , and evaluated the phenotype ofplanthopper resistance and agronomic characteristics related to rice yield. The results aresummarized as follows: 1. Linkage map construction: To alleviate the influence of segregation distortion onlinkage test and the estimation of recombination fractions, a three-step analysis wasemployed for map construction in this study. Firstly, the markers were assigned to eachrice chromosome according to the published maps. Secondly, Mapmaker 3.0b wasemployed to identify the most probable marker order within a linkage group. Thirdly,software QTXb19 was applied to verify the linkage among markers in the same group andestimate recombination fraction (R) between adjacent markers and the recombinationfraction (r) in BIL was calculated using the formular r= 2R/ (3-4R) and converted togenetic distance using Kosambi function. 2. QTL analysis: QTLs were determined by composite interval mapping (CIM) andmultiple interval mapping (MIM) of WinQTLCartographer version 2.0. A purtative QTLwas claimed when it was detected with a threshold of LOD>3.0 in CIM and displayedsignificant effect in MIM. Epistatic interaction between QTLs showing significant effectswas also detected using the software. Two QTLs for WBPH resistance were detected in theinterval RM305-RZ70 on chromosome 5 and RM215-RM245 on chromosome 9. TheDongxiang wild rice alleles could reduce seedling mortality by 15.30% and 12.22%, andexplained 14.9% and 12.5% of the phenotypic variation respectively. Two QTLs for BPHresistance were detected in the interval RG157-RZ551 on chromosome 2 and RG678-RM234 on chromosome 7. The Dongxiang wild rice alleles could reduce seedlingmortality by 1.60% and 3.12%, and explained 29.9% and 65.6% of the phenotypicvariation respectively. No epistatic interactions were detected between QTLs. 3. Genetic drag analysis: Genetic drag associations between QTLs for planthopperresistance and yield traits were analyzed. Genetic drag was observed between a QTL forplanthopper resistance and a QTL for spikelet fertility in interval RM164-RM305 onchromosome 5, and in interval RG451-RM215 on chromosome 9 between a QTL forplanthopper resistance and a QTL for filled grains per panicle.
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