| Rice is one of the most important crops in the world which is infected by all kinds of diseases and insects in the whole growth duration. Rice blast caused by Pyricularia grisea is one of the most serious diseases for rice yiled decrease. It has been proved that developing resistant varieties of rice is the most effective method to control this disease. A lot of superior rice germplasm were reserved in Yunnan province, one of the origin of Oryza sativa L., due to its unique climate. SB70, a native variety of Yunnan, is an excellent resistance resource to rice blast. Analysis of four resistance trait lesion degree, lesion length, lesion number and diseased leaf area to rice blast in SB70 and mapping the resistance genes on a molecular marker linkage map were performed in this study. All the results are showed as follows:1 One hundred and thirty-one double haploid lines were constructed from the anther culture of the combination SB70/ZS97 Fl progeny. The results showed that the NH4+ /NO3- ratio of 5.3/28 in induction medium could enhance anther culture ability; the carbon source with 3% maltose supplementing 3% sucrose could significantly increase frequency of callus induction; when anthers were treated with shock at 30 for 36 h, frequency of callus induction and green plant differentiation were increased to difference significance lever; frequency of callus induction and anther culture ability increased with spraying 0.8% KH2PO4 to donor plants.2 SB70 and a set of near-isogenic lines (NILs) for rice blast resistance were inoculated at seedling stage with 47 Pyricularia oryzae isolates. SB70 was found to be resistant to 41 of them and showed resistance similar to the wide spectrum resistance gene Pi2, and was resistant to all the isolates from Hunan, Hubei and Zhejiang provinces.3 Segregation ratio between resistance and susceptibility in SB70/ZS97 F2 population revealed a single dominant resistance gene against tested isolates in SB70; the inoculated results of F2 seeds from SB70 crossed with two sets of NILs suggested that the putative gene resistant to rice blast was different from the known resistance genes.4 A molecular marker linkage map was constructed by 137 SSR markers based on an F2 population of 282 plants derived from the cross between SB70 and ZS97. The map covered 1383.5 cM of the whole rice genome, and two markers spanned 10.1cM on average. The chi-square test showed 25 markers skewed from normal segeration ratio.5 Analysis of resistance spectrum and resistance heredity suggested there were two newgenes to rice blast in SB70, and the gene Pi-si against isolate 0413 was mapped on chromosome 6 embraced by RM204 and RM314 and the gene Pi-s2 against isolate 1829 mapped on chromosome 11 embraced by RM206 and RM254. The inculation results of seedling and adult stage showed the resistance gene Pi-si to isolate 0413 expressed in the whole growth duration.6 Twelve markers were correlated with lesion degree, lesion length, lesion number and disesed leaf area resistance to rice blast by single marker detection method, which can explained variance from 1.5% to 49.0%. After the 4 resistance traits to isolates 0413 and 1829 were assayed in entire genome by the method of interval mapping, two main effect QTLs were found to respectively explain 50.4% and 55.0% variance which were located in the inteval RM510-RM204 on chromosome 6 and the interval RM254-206 on chromosome 11. In addition 4 minor effect QTLs related with resistance were all detected.7 The results of composite interval mapping suggested that the positions of main effect QTLs to rice blast resistance was at the same positions as those detected by interval mapping method and some difference of minor effect QTL positions with the former.8 The epistatic interaction was analysised in entire genome and a total of 39 digenetic interaction marker pairs were found which contributed 6.41%-25.65% variance to genetic variation. It suggested that epistasis between non-QTL and non-QTL was the primary inte...
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