The Waterlogging Tolerance Evaluation And Preliminary QTL Mapping Of Traits Associated With Waterlogging Tolerance Of Cucumber

Cucumber (Cucumis sativus L.) (2n = 14) belonging to the family Cucubitaceae, is grown throughout the world and is the fourth most important vegetable followed tomato, cabbage and onion. Cucumber is increasingly attractive to plant breeders and farmers for its economically important value.In recent years, the natural enviroment changed greatly, and flooding broke out frequently especially in the southern China along the downstream of the Yangtze River. The Natural disasters brought great economic loss, and also affected the people's lives. So, it is urgently to find the mechanism of waterlogging stress response and get excellent waterlogging resistance germplasm. It has an important theory and realism sense for our country's agricultural development. To find the waterlogging resistance difference among cucumber cultivars, and get suitable index for identificating the waterlogging resistance of cucumber. To map quantitative trait loci (QTL) associated with waterlogging tolerance in cucumber, the waterlogging tolerant cultivar PW0832 and suspetible cultivar of PW0801 were hybrided to get the F1 line, and then 112 F2:3 family lines were construted. The major research results were as follows:1 Evaluation of the waterlogging tolerance among different cucumber cultivars.The 40 cucumber cultivars which at five-leaf stage were flooded by water which lasted 6 days. The samples were collected before and after the treatment. The death plant ratio, chlorophyll loss ratio, SOD, POD and CAT values were determined. By the correlation analysis, the coefficient values of the death plant ratio and chlorophyll loss ratio were 0.4051 which was significant. So, chlorophyll loss ratio of plant could be one important index which could evaluate the waterlogging tolerance difference among cucumber. By the comparision of death plant ratio and chlorophyll loss ratio among different cultivars, we found that the cultivar"Zaoer N","Zhenong","Ningyang 7"with high tolerance to waterlogging stress, and the cultivars"W119"and"Pepino"were susceptible to waterlogging stress. Base on the affiliation function analysis, the affiliation function values of"Zaoer N","Ningyang 8"and"Ningyang 2"were higher than other culitivars, and"W119"and"Holand cucumber"were lower. Combining the correlation analysis with affiliation function analysis, we could found that"Zaoer N"was waterlogging tolerant cultivar, and"W119"was susceptible.2 The QTLs mapping of traits associated with waterlogging tolerance of cucumber.A set of 112 F2:3 families which were bred by PW0832 and PW0801 were used to evaluate the adventitious root formation and chrolorphyll loss ratio using a random complete-block design. A genetic linkage map containing 30 ISSR markers and 32 SRAP markers were constructed, spanning a total of 992.2 cM, with an average interval of 16.0 cM. 2 QTL were found to be associated with adventitious root formation, and 1 QTL was associated with chrolorphyll loss ratio by using of composite interval mapping (CIM) method. The detected regions need to be mapped detailly, however, the QTLs found in this study could provide useful information for future genetic studies in cucumber waterlogging tolerance.