Genetic Analysis And Mapping Of Cca-2Gene Resistant To Cucumber Target Leaf Spot

Cucumber target leaf spot, caused by Corynespora cassiicola（B.&C.）have resulted in increasinglosses in cucumber production in recent years．Thus far, research about cucumber target leaf spot isprimarily focused on identification, controlling methods and biological characteristics. Study oninheritance and molecular makers related to this resistant gene is much less. Furthermore, inheritancereported is inconsistent. In this study, wide cross PI183967×931and their progenys F₁、F₂、BC₁P₁、BC₁P₂are used for genetic analysis by inoculating conidia suspension in seedling stage. Simplesequence repeat（SSR）techonology, Bulked segregation analysis（BSA）and genetic map are employedto mapping cca-2gene of cucmber in F₂population. Moreover, candidate genes are predicted accordingthe cucumber genome sequence, and verification is conducted in21cucumber lines. The results arelisted as follow.（1） The genetic analysis showed resistance to cucumber target leaf spot is controlled by a singlerecessive nuclear gene.（2）64SSR and1ESR-SSR primers are obtained by screening from the BSA pools. A linkagegroup corresponding to chromosome6of cucumber is constructed, containning39SSR,1EST-SSRand gene cca-2. cca-2is mapped between SSR10954and SSR16890, with genetic distance0.6cM and1cM respectively.（3） A cucumber genetic map is constructed, with99SSR markers in seven linkage groups spanning829.7cM, the average genetic distance is7.8cM. A QTL with10.9%variance explained is detected onsite SSR17624in chromosome6of cucumber.（4）180candidate genes are predicted during1254.7kb cucumber genome sequence betweenSSR21318and SSR18780, of which21candidate genes are related to plant disease resistance.（5） The accuracy rate of SSR10954and SSR16890verified in21cucumber lines are both85.7%，which facilitate marker-assisted selection（MAS） for cucumber breeding.