Genetic Analysis And Preliminary Mapping Of QTL_s Associated With Dwarf Trait Of Cucumber (Cucumis Sativus L.)

Cucumber (Cucumis sativus L.) is one of Cucubitaceae, which collectively belongs to a group of vegetables known as cucurbits and stands the fourth place followed by tomato,Chinese cabbage and onion. The plant height is one of important agriculture characters. Cucumber can be divided into two types.One has a long vine and the other short vine called dwarf type.Different vine types of cucumber might meet the need of the development of protected cultivation.The dwarf cucumber is easy to be cultivated in greenhouse since it is cost saving through cancelling a kickstand and increasing plant density. Tthe special superiority of dwarf cucumber has the broad application prospect in the production. Therefore, cucumber breeders are attaching importance to the breeding of new cucumber variety with reasonable plant height.Genetic analysis for cucumber plant height has been carried out with the method of quantitive traits heredity mode by using the commix model of main gene and multiple genes. F2 population from the cross combination of the dwarf line D8 and the vine line JIN5 were used in this study to screen the molecular marker related to the dwarf gene of cucumber with ISSR marker and BSA(bulked segregation analysis) method. A molecular linkage map was constructed with ISSR and SRAP marker. QTL ananlysis of plant height, flowering date of first female flower and the resistance to powdery mildew was performed with composite interval mapping(CIM). The main results are as followe:1. Six generations of P1 P2 F1 BC1 BC2 and F2 from the cross of dwarf line D8 and vine line JIN5 of cucumber were obtained to analyze the genetic effects of plant height by method mentioned above. Results indicate that the heredity of plant height could be explained by an additive-dominance major genes and additive-dominance polygene model ,and mainly by the main gene. In cucumber breeding, the selection in early generations may be effective.2. The F2 population from the cross between dwarf line D8 and vine line JIN5 was employed to screen the molecular marker related to the dwarf gene of cucumber with ISSR marker and BSA(bulked segregation analysis) method. UBC818, one out of eighty ISSR primers, was screened to present polymophism specified in the dwarf line. Genetic analysis showed that the genetic distance between the specific marker and cucumber dwarf gene was 11.1 cM. Two primers were designed based on the sequence to transform ISSR marker into SCAR marker. The ISSR marker was successfully converted into a SCAR marker named UBC818-S. This SCAR marker could distinguish the vine plant and dwarf plant accurately, easily and time saving, which provided a scientific basis of the marker-assisted breeding for dwarf cucumber.3. A genetic linkage map containing ISSR and SRAP markers was constructed, spanning a total of 831.6cM with an average interval of 12.7cM. The minimum heredity distance is 4.8cM, the maximum heredity distance is 22.3 cM. With the method of composite interval mapping and WinQTLCart2.5 software, two QTLs of plant height were examined, one QTL of the average distance nodes was identified. Moreover, seven QTLs of flowering date of first female flower were located.The QTL found in this study could provide useful information for future breeding of the plant height in cucumber.