Genetic Mapping Of Ll2, A Major QTL Controlling Leaf Area In Cucumber (Cucumis Sativus L.)

Cucumber (Cucumis sativus var. sativus), diploid plant (2n= 2x= 14), provides medicine and food for consumers in the world. Leaf is an important organ of photosynthesis. Leaf area affects the efficiency of photosynthesis and is one of the main crop yield traits. The research of the major QTL controlling leaf area in cucumber contributes to the cloning of the gene, revealing the mechanisim of cucumber leaf development.Previously, a major gene ll(little leaf) controlling leaf area was mapped on Chromosome 6 in cucumber. In this study, F2 population of 205 individuals segregating at leaf area was developed from the two cucumber lines including "XF-24" (little leaf) and "DF-32" (large leaf). After that, phenotype and genetics of cucumber leaf area trait were analyzed, a genetic linkage map was then constructed with the InDels screened in pools and parental lines, and finally the major QTL controlling leaf area was further analyzed.The main research results are as follows:(1) The investigation on the leaf area of F2 population and SAS software data analysis showed that measured value of leaf area of F2 population conformed basically with normal distribution, suggesting leaf area also belong to typical quantitative trait inheritance.(2) After the construction of gene pools by BSA method, combined with the re-sequencing information of the parents of F2 population,7 InDel markers, InDel-1, InDel-2, InDel-3, InDel-4, InDel-5, InDel-6 and InDel-7, were identified on Chromosome 7 of cucumber genome. Molecular linkage map which was drawn with JionMap4.0 software showed that all the 7 markers were located on the fragment of linkage group, and the distances of adjacent markers were respectively 1.1 cM,3.1 cM,2.2 cM,5.1 cM,4.8 cM and 5.8 cM. The total length of the fragment of linkage group was 22.1cM and the average distance of adjacent markers was 3.7 cM.(3) 112, A major QTL locus of leaf area in cucumber, was found at 4.2 cM from the top of chromosome 7 of cucumber genome, between InDel-2 and InDel-4, through the construction of genetic linkage map and QTL analysis. The LOD value of 112 was 10.57. And 21.1% of phenetic variation was interpretated. The size of the mapped interval of the trait was 5.3 cM, while physical distance was 1.24 Mb.