Construction Of Cucumber Chromosome Introgression Lines And Location Of Main Fruit Qtls

Wild sour cucumber (Cucumis hystrix Chakr.) is the progenitor of cultivated cucumber (Cucumis sativus L.) with small leaves, many branches, spherical fruits and strong disease resistance which contains abundant genetic diversity. It’s of great significance to braden the genetic basis of cultivated cucumber to find good genes from the wild cucumber for the cultivation of cucumber varieties. The wild cucumber with small fruit, thick skin and black thorn is phenotypically less desirable in its overall appearance and performances. The favorable alleles are usually linked with the undesirable genes in wild germplasm. It cannot be used as immediate material in breeding. So it’s a great convenience to take full advantage of the excellent genes in the wild sour cucumber by constructing a set of cucumber-sour cucumber chromosome introgression lines using the wild sour cucumber and cultivated cucumber by interspecific hybridization.1. Construction of chromosome introgression lines with the background of cultivated cucumberIn this study, we got allotetraploid materials using the North China cultivar cucumber ’Beijingj ietou’as recurrent parent and the wild sour cucumber as donor parent by the way of interspecific hybridization and embryo rescue techniques. On this basis, we constructed a set of50chromosome introgression lines by the way of multi-generation backcross selfing and molecular marker assisted selection. In the lines, we detected149chromosomes introgression fragments, including61different introgression clips. The total length of the different imported fragments is259.95cM and the coverage of the cucumber genome is45.37%. The length of introgression fragments is between1.65～15.4cM with the average5.41cM distributing in7chromosomes of cucumber. 2. Constrution of a genetic linkage map using the cultivated cucumber-wild sour cucumber introgression linesWe constructed a genetic linkage map consisting of109SSR markers, covering572.9cM in cucumber genome, by the cultivated cucumber-wild sour cucumber introgreesion lines, with an average interval of5.26cM. The linear order of the SSR markers in the map was in good agreement with that pubulished previously.3. Mapping QTLs related to main fruits traits using cucumber-wild sour cucumber CSILsWe used single marker analysis to identify QTLs related the fruits traits in the50lines of the cucumber-wild sour cucumber CSILs. Three traits were evaluated i.e. the fruit length, fruit diameter, the ratio of fruit length/diameter. The results showed that coefficient of variation among different introgression lines were25.99%,14.55%and28.57%.13QTLs were detected by one single marker anlysis and t-test, of which3QTLs were related to more than one trait. The results showed that some of the mapping QTLs from wild sour cucumber is detrimental gene. It means that a large mumber of favorbable genes carried by the wild sour cucumber may be linked with unfavorable gene. It’s a further research subject how to break the linkage.