| Bacterial wilt, caused by the soil-borne bacterial pathogen Rolstonia solanacearum is one of the most devastating bacterial plant diseases, occurs mainly in tropical and subtropical areas, but also in warm and even in cool temperature regions. It affects more than 200 plant species distributed in about 50 families including many economically important crops such as potato, tomato, eggplant, and tobacco. Various methods have been employed for the control of this disease such as agro-chemicals and other integrated agronomic measures, but ultimately they have been demonstrated to be ineffective in practice. Developing resistant cultivars therefore remains the most desirable target for economical and effective control. At present, there are no resistant genes found in tetraploid cultivars, but some wild species or their cultivated relatives, are known to be resistant to bacterial wilt and thus are potential sources for resistance. Solanum phureja displays high degree of resistance to Rolstonia solanacearum and has been used as a major source of bacterial wilt resistance in potato breeding. However, the precise inheritance model of resistance remains unknown because the expression of resistance varies with interactions between the environment and R. solanacearum strains. This reduces the efficiency of screening for resistance in field and slows down the development of new resistant cultivars. In recent years, with the advent and development of molecular marker, marker assisted selection has been utilized as a viable method for improvement of disease resistance in crops. The development of molecular markers linked to the resistance gene would facilitate its introgression in backcrossing programs and direct selection of disease resistance materials without arduous field-testing. Also, it opens the possibility of cloning the resistance genes via map-based cloning and direct target gene transformation.In this paper, bacterial wilt resistance segregation analysis was performed by field disease resistance testing of the two related segregating populations, CE and ED, which were generated from a highly resistant primitive cultivated specie Solanum phureja and wild specie Solanum vernei, and bulked segregant analysis was used to identify random amplified polymorphic DNA (RAPD) markers linked to bacterial wilt resistance in diploid potato. The major results are as following:1. Field disease resistance testing data of genotypes of the CE and ED populations to Rolstonia solanacearum race 1 (biovar 3) indicated that bacterial wilt resistance of the CE and ED populations fitted into 1:1 segregation ratio, which was confirmed by chi-square test. It facilitated analysis of markers cosegregation with resistance.2. Combined with bulked segregant analysis, we screened 160 random 10-mer oligonucletide primers, of these, OPA07446 and OPA12980, were found to link to bacterialwilt resistance. In the ED population, the map distances between the two markers and the resistance locus were 14.7 and 24.7 cM for OPA07446 and OPAllggo, respectively. Further linkage analysis showed that the two RAPD markers bracketed the resistance locus as flanking markers with a map distance between them of 39.4 cM. In the CE population, the map distances between OPA07446, OP A12930 and the resistance locus were 23.9 and 31.4 cM, respectively.3. Compared the accuracy of single marker and double markers selection, we observed that, the accuracies of selection of OPA07446 and OPA12980 were 85.7% and 75.7% respectively for the selection in the ED population, and 77.8% and 72.2% in the CE population when they were used alone. However, the selection accuracy increased to 95.7% in the ED and 95.0% in the CE population when the two markers were also used. Based on this, a double flanking marker selection strategy in MAS was proposed.4. After extracting, cloning and sequencing of the specified amplified RAPD products, OPA07446 and OP A12930, were converted into sequence characterized amplified region (SCAR) markers with the designed SCAR primer. SCAR an...
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