| Bacterial Blight(BB), caused by Xanthomonas oryzae pv.oryzae(Xoo), one of the most devastating diseases of rice through the world, is a serious problem of hybridization rice production in China. The usage of resistant genes was considered the best strategy for controlling the Bacterial Blight. But, because of the resistance genes in rice being single, the tendency of rice becoming susceptible to BB has been rising in recent years in China. There were many studies had indicated that the gene pyramiding is an effective strategy in developing varieties with durable resistance. Marker-assisted selected (MAS) has been advocated as a highly efficient breeding method in pyramiding genes, because it can offer rapid and precise selection of the targeted genes. The object of this study was to advance a more effective system of marker-assisted selection and improve the Bacterial Blight resistance of two restorer lines, "Shuhui881"and "Mianhui725", by pyramiding two dominant and highly resistant genes, Xa21 and Xa4, from 1RBB60, into it through MAS and traditional breeding technology. The STS marker pTA248 and SSR marker M55, tightly combined with Xa21 and Xa4, respectively, were used to marker-assisted select during the breeding. Through 3 years, the two resistant genes were pyramided into the two restorer lines, and a new effective system of MAS was also established. The main results are following:1 .A new rapid and economical DNA extraction system was established. The PCR result indicated that it is better than the large-scale and mini-scale method, both the quality and quantity of DNA from this extraction system are enough for marker-assisted selection.2.The polymorphism analysis indicated that pTA248 and OSR6, highly combined with Xa21 and Xa23 respectively, can be used to marker-assisted select between IRBB60 and the 11 hybridization rice parents in this study, and M55, highly combined with Xa4, can be used to marker-assisted select between IRBB60 and 9 hybridization rice parents except "Yihuil577" and "Yanhui559" in this study.3.Using 365 SSR markers to analysis the polymorphism between IRBB60 and 'Shuhui881"and "Mianhui725"through the whole genome. The result showed that there werev56 polymorphism SSR markers between IBBB60 and "ShuhuiSSl", while 58 polymorphism SSR markers between IRBB60 and "Mianhui725". We can use it to undertake background selection and genome background analysis.4.By the marker-assisted select and traditional breeding technology, through continuous self-cross and back-cross, we had obtained 70 and 57 plants containing Xa21Xa21/Xa4Xa4 and agricultural traits being similar to "ShuhuiSSl"and "Mianhui725"respectively.5.Random selected 10 polymorphism markers between donor parent and acceptor parent to undertake background select in every selection generation and obtained 39 and 40 plants in "ShuhuiSSl"and "Mianhui725"respectively, the similarity between the parents was above 90%.6. The polymorphism markers in the whole genome were used to analysis the genetic background of 22 plants from the result 5. It showed that the similar ratio of genetic background to "ShuhuiSSl" ranged from 91.07% to 100% and the similar ratio of genetic background to "Mianhui725"ranged from 91.38% to 100%.7.The population having Xa21 and Xa4 and the population having single Xa21 and single Xa4 were inoculated by P6 and PI respectively. The result indicated that the lesion length of the pyramiding lines was marked shorter than the single gene lines. We can come to the conclusion that genes pyramiding can enhance rice's resistance to Bacterial Blight.S.The resistance spectrum analysis by using Abo strains C1-C7 indicated that pyramiding Xa21 and Xa4 can improve rice's resistance spectrum to Bacterial Blight.9.1n order to estimate the accuracy of MAS with pTA248 and M55, we selected 180 plants having single resistant gene Xa21 or Xa4(each gene type 60) from BC2F2 constructed two estimate population and inoculated by P6 or PI respectively. The result indicated that the accuracy of pTA248 sel... |
PDF Full Text Request