Genetic Analysis Using Mixture Model Of Major Gene Plus Polygene And QTL Mapping For Leaf Area In Cucumis Sativus L.

Leaf size is one of the most important parameters in determining optimal shoot architecture of cucumber. On the one hand, as the major photosynthetic organ, size of leaves can affect final fruit product. On the other hand, it also determines planting density which also affect final production. To investigate how cucumber leaf size is genetically determined,two parents with significantly different leaf size,namely ?SJ57-h?(plant with small leaves,?P1? hereinafter) and ?SJ11-1?(plant with big leaves,?P2? hereinafter),were used to generate F1、B1、B2 and F2 populations. These populations were used for joint analysis using mixed major gene plus polygene inheritance model in different seasons. To develop genetic markers for marker-assisted breeding, SSR markers were screened and a likage map was constructed. Besides genetic analysis, microstructures of big leaves and small leaves was examined by paraffin sectioning, and leaf size variation on whole plants were also determined.Main results are as follows:(1) Cells of the parent with big leaves were bigger than that of small leaves, and its arrangement was quite loose.(2) For one plant, leaves at bottom(1st- 4th) and top(16th and above) were relative small, and those between 5th- 15 th had the largest leaf size. So the general tendency of leaf size variation in whole plant was(from bottom to top) small- big- small.(3) The leaf size was controlled by two additive-dominant-epitasis major genes plus additive-dominant-epitasis polygenes(E-0 model). Leaf size was closer to P2(big size). In spring,the major gene heritability of B1, B2 and F2 were estimated to be 75.1%、26.59% and 61.19%,respectively,with the heritability of polygene as 0.36%、55.41% and 21.39%,respectively. The variance of the environment accounted for 25.03% 、 73.79% 、 39.01% of the phenotypic variation of three generations, respectively. In autumn, the major gene heritability of B1,B2 and F2 were estimated as 80.16%、34.82%、86.59%,with the heritability of polygene being 0、49.18% and 0,respectively,and the variance of the environment accounted for 20.43%、65.48% 、 13.51% of the phenotypic variation, respectively. It indicated that cucumber leaf size was dominated by major genes while environment factors also play a great role,espcially on the B2 generation. In practice,high hereditability of major genes is favorable to an efficient selection in early generation of F2 and B1 for suitable leaf size in cucumber breeding.(4) 117 pairs of SSR primers in the DNA of two parents and between the pool filter, and F2 groups after a single authentication 177, the 3 SSR and cucumber leaves the area of the relevant markers. the distance between markers were 9.0c M and 16.9c M, the total length of linkage groups 25.9c M, the average distance between markers 8.6c M.(5) Preliminary positioning through QTL analysis, detected with a cucumber leaves area QTL related sites, located in the genetic map of linkage, specific at SSR01012-Qchl1-SSR01784 between the primers, and SSR01012 closer distance for the 2.6 c M, the corresponding LOD value of 1.67, 9.63% explain the genetic variation.