| The virus disease is the main disease affecting the production of cucumber, which is difficult to control. There are many different kinds of pathogens. Watermelon mosaic virus(WMV) and Papaya ring spot virus(PRSV) are the two main pathogens causing virus disease. For the resistance genetics and gene mapping of WMV and PRSV, the F2 population and F2:3 families, which were developed from the cross between susceptible ‘65G’ and resistant ‘02245’ cucumber inbred lines, were inoculated by gentle rubbing and established by ELISA. Several candidate genes related to WMV resistance were selected to study the expression profile by real-time PCR. The results are as follows:1 According to the inoculating data, the segregation ratios of the F2 population fitted the 3:1. Therefore, the genetic analysis confirmed that WMV and PRSV resistance were conferred by a single recessive gene, respectively.2 Among 1,288 SSR markers tested, 296(22.98%) were polymorphic between ‘65G’ and ‘02245’, of which, 6 SSR markers related to WMV resistance and 10 SSR markers related to PRSV resistance,respectively, were obtained through BSA method. wmv and prsv genes were both mapped in cucumber chromosome 6. The flanking markers SSR01566 and UW016108 were linked to wmv gene with genetic distances of 6.4 cM and 3.9 cM. The prsv gene was flanked by two SSR markers, SSR18405 and SSR33284 with 7.1 cM and 10.6 cM away from the prsv locus.3 For further mapping of the prsv gene, new markers were designed. Then, linkage analysis identified two closer markers, SSR11-177 and SSR11-1 flanking the prsv locus with genetic distances of 1.1 cM and 2.9 cM, respectively. The physical distance between the two markers was approximately 602.9kb. Marker verification showed that the accuracy rate of SSR11-177 in 35 different cucumber lines was 82.9%.4 For high-resolution genetic mapping of wmv, we constructed an F2 population of 1921 plants and narrowed down the wmv locus to a 134.7kb region flanked by CAPS-W1 and SSRWMV60-23 with genetic distances of 1.19 cM and 0.34 cM. Marker verification showed that the accuracy rate of SSRWMV60-23 in 70 different cucumber lines was 94.3%.5 Gene prediction was applied through the bioinformatics technology. The result showed that 21 genes were predicted in this region, including 16 with function annotation, of which, 4 candidate genes relative with disease resistance.6 Cucumber leaves with WMV inoculation after 0h, 16 h, 40 h, 3.5d, 5.5d and 8d were collected to extract RNA and applied for real-time PCR analysis to 4 candidate genes. The result showed that the relative expression of a transcription factor related to the ethylene biosynthesis presented increasing in resistant parental material within 40 h after inoculation, whereas, there was little difference between susceptible lines. According to our data, the transcription factor gene PR-TF is likely to confer the WMV resistance in cucumber. |
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