| Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) and rice blast caused by Magnaporthe grisea are two critical diseases in rice. Developing resistant cultivars is one of efficient strategy to control these diseases. Introducing resistance genes into the objective cultivars by molecular marker-assisted selection (MAS) technology to develop certain high yield, multi-resistance and good quality lines has great practical significance in rice breeding. In present paper, based on introducing BB resistance gene Xa23 and blast resistance gene Pigm, these genes were incorporated into rice restore line with MAS and detected by EST marker C189 linked with Xa23 and marker M26205 based on the Pigm sequences respectively.The BB resistance gene Xa23, which is carried in the donor parent 18113, was introduced into the intersubspecific restore line H705 and good quality restore line H706 by crossing and MAS. Seventy-one and 52 lines carrying homozygous gene Xa23 derived from the 18113/H705 F3 and 18113/H706 F3 lines, were obtained based on the PCR test with EST marker C189 respectively. The BB resistance expression of these materials was inoculated and identified with pathotype IV representative strain, Zhel73 by clipping method. Sixty-one and 44 lines from the two combinations were demonstrated with the BB resistance, and their MAS accuracies were 85.92% and 84.61% respectively. The C189 was one of the effective MAS markers for testing Xa23 gene; the mechanisms which caused false positive rate is higher than theoretical exchange rate remain elusive.The blast resistance gene Pigm, which is carried in the donor parent GM4, was introduced into the restore lines by pedigree method and MAS. Based on the PCR test with M26205, only eight materials out of a total of 118 rice germplasms collecting from 14 countries were amplified an 800bp band. Others could not amplify any bands. Nine lines out of 49 derivate lines developing from eight combinations of GM4(Pigm gene donor) and restore lines (susceptible cultivar) were demonstrated carrying homozygous Pigm genotype. The evaluation of rice blast resistance of 9 homozygous Pigm genotype to nine virulent races from Zhejiang using artificial inoculation was carried out, results showed nine lines are resistance or moderately resistance to rice blast. The analyses of agronomic traits for nine lines hinted that introducing Pigm has a negative effect on tiller numbers and grain weight, but a positive effect on grain numbers of panicle and seed set. Twelve lines carrying double resistance genes from the crosses of D3(Pigm homozygous genotype) and FH450(Xa23 homozygous genotype) were obtained by PCR test with M26205 and C189. The following evaluation of disease resistance and agronomic traits are under way.To identify and distinguish the similarities and differences of species using DNA molecular markers has very important meaning to breed new varieties and to set up their fingerprinting. Twelve pairs of PCR primers were selected from 12 chromosomes to amplify the genomic DNA of F4 lines from 18113/H706 and their parents. A total of 69 bands were obtained, of which 49 were polymorphic, accounting for 71.01%. The dendrogram based on bands amplified by SSR marker and based on phenotypes of fifteen agronomic traits showed that tested materials can be divided into four groups and ten subgroups, five groups and thirteen subgroups. It was similar or different categories that the same samples genetically cluster through two kinds of method former mentioned so whether these twelve SSR markers can distinguish or identify varieties in rice need more studies. |
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