Study On Traits Analysis And SRAP Molecular Markers Of Fruit Dehiscence In Mini-watermelon(Citrulls. Lanatus)

Using the RI group of mini-watermelon as experiment material, statistical analyse8fruit traits of watermelon such as fruit diameter longitudinal, fruit shape index, pericarp thickness, the green layer thickness of exocarp, content of center sugar, content of edge sugar and fruit-dehiscence, and explore the correlativity between the main fruit traits and fruit-dehiscence, to provide certain theoretical basis and reference for the search of dehiscent mechanism and dehiscence resistent breeding of watermelon. Constructing watermelon molecular genetic map with method of SRAP molecular marker by using the95plants of RI group, to lay the fundations for the establishment of saturated watermelon genetic map, QTL mapping of important agronomic characters and cloning and locating of important gene. The main results of this experiment were as follows:1. The results of variance analysis showed a significant difference in the8characters. The results of correlation analysis showed that there is no significant correlation between the fruit-dehiscence degree and the other characters. There is a positive correlation between fruit diameter, the green layer thickness of exocarp, content of center sugar, content of edge sugar and fruit-dehiscence, and a negative correlation between longitudinal diameter of fruit, fruit shape index, pericarp thickness and fruit-dehiscence.2. The test results showed a model of optimal regression equation by stepwise regression analysis, Y=19.539-9.476X3-15.699X4-70.537X5+3.864X7(R=0.32), the F value is2.5672by the analysis of variance, it is significantly different at the0.05level. This regression equation can be used to accurately predict. The degree of influence on fruit-dehiscence from large to small is:the green layer thickness of exocarp> pericarp thickness> fruit shape index> content of edge sugar.3. Four fruit traits such as fruit shape index, pericarp thickness, the green layer thickness of exocarp and content of edge sugar had direct and indirect effect on fruit-dehiscence by path analysis, the effect value was between0.1334and0.1857. The direct effect of fruit shape index on the fruit-dehiscence degree is maximum, and the decision coefficient is0.10241, the residual path coefficient is0.94741.4. Most of the OD260/OD280value of the genomic DNA sample of watermelon extracted by improved CTAB method. 5.418pairs of SRAP primer combinations are used in the test for polymorphism amplification, and there are91pairs of primers which could amplified polymorphism bands, the polymorphism is21.8%. Only29of91pairs of primers for amplification in the RI group amplified stable and clear polymorphism bands.6. Use of48polymorphic loci which produced by the selected29pairs of primers on watermelon molecular genetic map construction. This map contains5linkage group, and the total length is302.9cM, the average distance between two tags is20.2cM. The largest group in the map are c2and c5, which including4tags, and their length are56.9cM and95.4cM. c4is the smallest linkage group, there is only2tags and the length is22.5cM.