Genetic Mapping of the Scab Resistance Gene in Cucumber

Abstract

Scab, caused by Cladosporium cucumerinum Ell. et Arthur, is a prevalent disease of cucumber (Cucumis sativus L.) worldwide. Scab can cause serious losses for cucumber production, especially in protected culture such as high tunnel production. Resistance to cucumber scab is dominant and is controlled by a single gene, Ccu. Breeding for resistant cultivars is the most efficient way to control the disease. Selection for resistance might be made easier if the gene were mapped to linked markers. Thus far, there are no tightly linked (genetic distance less than 1 cM) simple sequence repeat (SSR) markers for the Ccu gene, and no studies on mapping of the Ccu gene in cucumber using SSR markers. The objective of this study was to identify SSR markers for use in molecular breeding of scab resistance. In this study, we used a population of recombinant inbred lines (RILs). The population included 148 individuals derived from the cucumber inbred line 9110 Gt (Ccu Ccu) crossed with line 9930 (ccu ccu). The Ccu gene was mapped to linkage group 2, corresponding to chromosome 2 of cucumber. The flanking markers SSR03084 and SSR17631 were linked to the Ccu gene with distances of 0.7 and 1.6 cM, respectively. The veracity of SSR03084 and SSR17631 was tested using 59 diverse inbred lines and hybrids, and the accuracy rate for the two markers was 98.3%. In conclusion, two SSRs closely linked to scab resistance gene Ccu have been identified and can be used in a cucumber breeding program.