| Finding novel beneficial genes from rice germplasm, widening rice genetic variability, gene mapping and inheritance studies of new genes by means of classical and molecular tools, have always provided basis for the rice breeding. Of these major objectives of rice breeding and genetics studies, the exploitation and mapping of new resistance genes have always attracted great attentions of rice breeders and geneticists. Finding and mapping of new genes conferring resistance to the whitebacked planthopper, Sogatella furcifera and determining its genetic mechanism, could widen the genetic variability of rice for preventing the genetic vulnerability due to a narrow genetic background, establish novel techniques,for resistance identification, and provide basis for marker assisted selection of resistance to S. furcifera, cloning of the resistance genes and comparative genomics studies.Resistance evaluation, classical genetic study, allelism analysis and molecular mapping were conducted in this study for the exploitation rice germplasm for S. furcifera resistance and mapping of new S. furcifera resistant genes. Seventy-six germplasms showing resistance or highly resistance to S. furcifera were selected. The inheritance of reisistance of 16 germplasms including rice landraces Guiyigu and Biangu from Yunnan Province was studied. A new gene Wbph6(t) from Guyigu showing potential application in rice breeding was found. The resistance gene Wbph6(t) was mapped on to the short arm of chromosome 11 of rice, with a genetic distance of 21.2 cM from SSLP marker RM167.1. Screening for Resistance to S. furcifera in New Rice GermplasmsBased on preliminary screening test, the resistance of 312 traditional rice varieties and 81 improved rice varieties with the resistance to S. furcifera were further screened using bulk-screening test. The results revealed that 16 rice germplasms were highly resistant to S. furcifera, and 60 rice germplasms resistant to S. furcifera, respectively.2. Genetic analysis of Resistance to S. furcifera in New Rice GermplasmsThe genetics of the resistance to S. furcifera in 9 improved rice varieties and 7 traditional rice varieties with good agronomic characteristics such as Guiyigu in rice germplasms was analyzed classically. The inheritance of the resistance in 11 rice varieties such as Guiyigu, Biangu, Daqigu, Dahuagu, HA79317-7, Dianrui336-3, Shiyazhan, 5006, Zhenongda6022, 9234, Zhongjian96-3 was governed by a single dominant gene and in 5 rice varieties such as Nongxiang16, R40, Shuhui881, Baigannuo and Nabeshi by a recessive gene.3.Allelic Analysis of Resistant Genes in New Rice Germplasms Resistant to S. furciferaCompared with the known resistant genes to S. furcifera, the allelic analysis of the resistance in Yunnan traditional rice varieties of Guiyigu, Biangu, Daqigu, Dahuagu and the improved rice varieties of Dianrui336-3, HA79317-7 demonstrated that the resistant gene in HA79317-7 and Dianrui336-3 was allelic with Wbph1 and Wbph2, respectively. Four Yunnan traditional rice varieties of Guiyigu, Biangu, Daqigu and Dahuagu possessed the same single dominant gene which is not allelic with the known genes Wbph1, Wbph2, Wbph3 and Wbph5, naming it as Wbph6(t).4. Preliminary mapping of new S. furcifera resistance gene Wbph6(t)An F3 population was constructed from a cross using international standard susceptible rice line TNI as female parent and landrace Guiyigu from Yunnan Province carrying Wbph6(t) as the male parent. By using of RFLP (restriction fragment length polymorphism) and SSLP (simple sequence length polymorphism) markers, the gene Wbph6(t) was mapped on to the short arm of chromosome 11 of rice. The genetic distance and recombination value between Wbph6(t) and RM167 were 21.2 cM and 20 % + 0.8%.5. Tagging Wbph6(t) to more closely linked markers and detection of markerslinked to other S. furcifera resistance genesAn F6 recombinant inbred line population of TN1/Guiyigu was constructed for the fine mapping S. furcifera resistance gene. Results indicated that S. |
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