| Sex differentiation in plants is a fundamental developmental process of economic importance.The diverse sex types of cucumber allow this organism to serve as a model system for studying sex expression in flowering plants. Primary genes that influence sex expression in cucumber has been described including F, M, A, In-F, gy, m-2, Tr. In addition, sex expression is also influenced by environmental conditions and plant hormones. Long days, high temperatures, and gibberellic acid promote the formation of male flowers, whereas short days, low temperatures, auxins, and ethylene enhance the development of female flowers. The model of sex determination in cucumber is presumed that ethylene serves as both a promoter of the female sex and an inhibitor of the male sex. The model predicts that the F gene encodes a molecule that influences the range and gradient of ethylene production along the shoot, thereby acting to promote femaleness, where as the M gene encodes a molecule that detects this ethylene signal and inhibits stamen development when ethylene levels reach a threshold. Recent studies have provided molecular evidence in favor of the ethylene model of sex determination in cucumber: the F gene encodes an ACC synthase, is cloned. The result is accord with above ethylene model of sex determination. In addition, the product of the M locus mediates directly the inhibition of stamen development by ethylene. For further testify the authenticity of the ethylene model, the M gene must be cloned and the molecular marker tightly-linked to the M gene is the basis of MAS and map-based cloning.In addition, it's significative in theory and production to research the MOA-Subgynoecious (monoecious-subgynoecious) gene since the subgyniecious importance in cucumber.In this study, by inheritance analyses and genetic mapping for sex-determing M gene and MOA-Subgynoecious QTL, we provide useful insight into sex-determing gene organization and function in cucmber, and our work makes the starting point for map-based cloning of the corralative gene and discovery of sex-determing mechanism in cucumber.The main results in this study are as follows:1. Nearly isogenic cucumber lines WI1983G (gynoecious; MMFF) and WI1983H (hermaphrodite; mmFF), F1 and BC1 individual plants were used as material to map M gene.The mother plant WI1983G bears only pistillate flowers, whereas the mother plant WI1983H bears bisexual flowers. All F1 progeny that were derived from the cross between WI1983G and WI1983H lines bore pistillate flowers. This finding confirmed the complete dominance of the maternal sex type over the paternal sex type. In the 751 BC1 individuals, 373 had only pistillate flowers and were scored as gynoecious (M_FF). In addition, 378 BC1 individuals had only bisexual flowers and were, thus, scored as hermaphroditic (mmFF). These results fit the Mendelian 1:1 ratio (χ2 = 0.03;p<0.05 ), indicating the single M locus controlled the segregation of the sex expression in the BC1 progeny. The result is consonant with the conclusion of others'study.2. We obtain three codominant markers, SSR19914, SCAR123 and SSR23487, were tightly linked to the M locus by the way of screening one SCAR and 2112 SSR primers. The M locus was flanked by the markers SSR23487 and SCAR123 that defined a 1.22 cM interval, while SSR19914 and SCAR123 at one side with genetic interval of 3.2 cM and 0.94 cM to M, and SSR23487 at the other side of 0.28 cM.3. Two segregating BC1 (188) and F2 (192) population were developed using the subgynoecious plant S-2-98 (monoecious type) as donor and monoecious plant 95 as recurrent parent. According to investigate the ratio of female nodes, the values of 188 BC1 and 192 F2 were all continuous distribution and fell between the parental values, indicating the absence of transgressive segregation in the two population. Which indicate the MOA-Subgynoecious traits were controled by multiple core gene.4. According software Joinmap3.0 and MapQTL4.0, based on analysing the parental plant S-2-98, 95 and BC1, F2 segregating population by bulked segregant analysis and 2112 pairs of primers, the high-density genetic map in cucumber and the ratio of BC1, F2 individuals'female nodes, we obtain 3 QTLs of MOA-subgynoecious (monoecious-subgynoecious) trait in chromosome 3 and 6 in cucumber.The three QTLs were named as Mod-F1a, Mod-F1b and Mod-F1c. Mod-F1a was located in chromosome 3 and it's genetic contribution rate was 49.8~54.6 %, Mod-F1b and Mod-F1c were located in chromosome 6 and their genetic contribution rates were 6.3~7.2% and 4.2~9.1%, respectively. The total genetic contribution rates of the 3 QTLs were 51.2~62.9 %.The additive effect of Mod-F1a and Mod-F1b were both positive, which indicate positive effects of the alleles were from S-2-98, whereas the additive effect of Mod-F1c was negative, which indicate positive effect of the allele was from 95. |
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