Analysis Of Parental Differences And Heterosis In F₁ Generation Of Watermelon Related Fruit Traits

Watermelon(Citrullus lanatus)is a major economic crop in China and also an important horticultural crop in the world.As the largest watermelon producer in the world,China has great development potential for watermelon variety optimization and breeding in the development process.However,the available watermelon germplasm resources are still under development.Therefore,it is necessary to avoid the low genetic diversity caused by the close relationship between different watermelon varieties,which leads to the slow development of watermelon germplasm resources,and the phenomenon that the excellent germplasm resources cannot be renewed and even the degeneration of watermelon varieties.After years of development,the forms of innovative research on germplasm resources include morphological markers,biological and biochemical markers,molecular markers and other means,which can provide better help to jointly reveal the diversity of germplasm resources.Subsequently,morphological markers are the study of the appearance and structure of plants and their organs,and the traits mainly used for labeling are some of the appearance and quality traits that can show genetic polymorphism.On the other hand,the study of genetic diversity using molecular markers can avoid the influence of external environment and other factors to the maximum extent,as well as show more abundant polymorphism.Both markers are widely recognized by breeders.Our study used the genetic diversity study of 30 watermelon hybrid combinations and its genetic diversity analysis on 26 copies of parent material,at the same time with the method of SSR molecular markers of 26 parent diversity analysis,and simultaneously to predict heterosis of 30 hybrid combinations,aim to the study of watermelon germplasm diversity,In order to reduce the selection range of watermelon and improve the efficiency of watermelon breeding.The specific results are as follows:(1)Variation analysis of 11 fruit-related traits including stalk length,stalk thickness and flower mark size showed that: The variation coefficients of the 11 fruit traits ranged from 9.43-53.62%,with an average variation coefficient of 25.49%.The highest variation coefficient was the flower mark size,which was 53.62%.The Shannon diversity index ranged from 2.27-2.93,with an average diversity index of 2.60.(2)Correlation analysis of 11 fruit related traits showed that there was a significant positive correlation between central sugar content and marginal sugar content,and the highest correlation was0.914.Vitamin C was significantly positively correlated with central and marginal sugar content.Stalk length was positively correlated with pericarp thickness.Single melon weight was significantly positively correlated with pericarp thickness and pericarp hardness,while organic acids were significantly negatively correlated with fruit shape index.The pericarp thickness was negatively correlated with central,marginal and vitamin C content.Pericarp hardness was significantly negatively correlated with central sugar content,marginal sugar content and vitamin C.(3)The results of principal component analysis on the selected materials showed that the 11 characters of the selected materials were divided into 4 principal components with the initial characteristic value greater than 1,and the cumulative contribution rate of the first 4 principal components was 72.80%.(4)Clustering analysis was conducted on the fruit related traits of 26 parent materials.The results showed that at the Euclidean distance of 25,the tested materials were divided into two categories:cultivation type and forage type.(5)Based on the traits of 30 materials and their parents,the heterosis indexes including high parental dominance and middle parental dominance were analyzed.The results showed that the heterosis indexes could be used to identify the hybrid combinations with high superiority in vitamin C,sugar content and other qualities.(6)Using SSR molecular markers and 23 pairs of core primers,polymorphism analysis was performed on 26 parental materials.The results showed that 593 bands were amplified by 23 pairs of core primers,and the size of the amplified bands ranged from 100 to 300 bp.Clustering results showed that the parent materials could be divided into two groups,the cultivated type and the forage type,at the similarity coefficient of 0.43.