Comparative Mapping Of The Dwarf Gene Bu From Tropical Pumpkin (cucurbita Moschata Duchesne) And Physiological Research Of Its Dwarf Character

Dwarf type is one of the most important agronomic traits, and the dwarf genes have been the focus of agricultural research. At present, study of dwarf genes in Cucurbits is still in the initial stage, and location and mechanism of dwarf type in Cucurbits is still less reported on. The cucumber genome provides a favorable platform for study of function of genes and cloning genes in Cucurbita. In this study, the association of various exogenous and endogenous hormones with dwarf was examined, and the dwarf gene Bu was mapped using comparative genomics on the basis of cucumber genome. Main conclusions are listed as follows:1. Dwarf pumpkin by spraying test with different concentrations of exogenous hormones( GA3, IAA, 6-BA and putrescine), the results showed that a variety of exogenous hormones could not make the dwarf pumpkin returned to the wild type; The dwarf plant and vine plant in C. moschata from BC9F2 population were tested in the endogenous hormones( GA3, GA4, IAA, ZR, JA-ME and ABA), and the results showed that the bush plant and vine plant in C. moschata had the similar levels of endogenous hormones. The two results indicated that dwarf mutant of C. moschata was not hormone-deficient but hormone-insensitive.2. The GA3 could significantly promote the elongation growth of petiole of dwarf pumpkin, but could not significantly for the elongation growth of main stem of dwarf pumpkin.3. The marker SCAR3-398 was tightly linked to Bu gene, and the specific fragment of the marker SCAR3-398 of squash was cloned and sequenced. The sequence of marker SCAR3-398 was blasted against the whole genome of cucumber, located in the region of telomerase of chromosome 5 of cucumber.4. We also developed three markers SSR19719, IF5-2 and IF5-3629 tightly linking to the Bu gene. These markers not only are useful in markers-assisted selection for bush plant, but also provide a solid basis for isolation of the dwarf Bu gene in squash.5. We also found three GA related genes (DELLA and GA20ox) at the end of chromosome 5 of cucumber. Coincidently, we found that one QTL locus of internode length of main stem of cucumber and the marker CSWTA04 linked to cucumber fruit handle length were also in the region of telomerase of chromosome 5 of cucumber.6. Based on these results, we propose the hypothesis that the dwarf mutant of C. moschata is related with the gibberellin.