Sugar Accumulation Regularity Of Watermelon Germplasm Resources And Quality Comprehensive Evaluation And Identification And Analysis Of Invertase Gene Family

Watermelon as an important melon and vegetable crop,juicy flesh,sweet and delicious,is the hot summer heat quenching thirst of the necessary good food.In China,a large number of new watermelon varieties have been bred with rich genetic germplasm.At the same time,an excellent germplasm resource can bring revolutionary changes to agricultural production,so it is necessary to strengthen the research and utilization of watermelon germplasm resources.Sugar is a crucial trait for watermelon germplasm and is a key index for screening germplasm materials in production.In this study,we used different ripening germplasm to study the regularity of sugar accumulation in watermelon,the relationship between nutrient composition in watermelon flesh and taste evaluation,and the identification and analysis of the invertase gene family in watermelon.The main conclusions are as follows:1、In order to study the sugar accumulation regularity of different mature watermelon germplasm resources,the soluble sugar composition in each stage of fruit development was measured.According to the sugar accumulation of different mature watermelon,at the early stage of fruit development,glucose and fructose were the first to accumulate,while sucrose content was less,and the accumulation rate was slow.At the late stage,with the decrease of glucose and fructose content,sucrose began to accumulate in large quantities;At the fruit ripening stage,the soluble sugar in most of the 28 watermelon fruits was fructose,followed by glucose,and sucrose was relatively low;Early maturing watermelons can be divided into fructose accumulation type and sucrose accumulation type according to their sugar composition at the full ripening stage.In sucrose accumulation type,sucrose content was as high as 40%～54%,while in fructose accumulation type,sucrose content was only 29%～36%;Since the sucrose content of middle and late maturing watermelon materials kept rising during the whole fruit development stage,it was speculated that the sugar composition of middle and late maturing watermelon materials might be similar to that of early maturing watermelon materials at the full ripening stage.2、In order to explore the key factors that determine the taste of watermelon,the physiological indexes of 10 early maturing watermelon materials were determined,and the correlation analysis with the taste evaluation was carried out.At the same time,the membership function method was selected to comprehensively analyze the nutritional indexes of watermelon.The results showed that total sugar content,soluble solids,vitamin C,soluble protein and cellulose were significantly or extremely significantly positively correlated with taste evaluation,lycopene was positively correlated with taste evaluation,and water content and organic acid were significantly negatively correlated with taste evaluation;In addition,the evaluation results of membership function method are basically consistent with the evaluation results of taste,when the membership function > 0.6,the watermelon taste is better;the most significant factors affecting fruit taste include soluble solids,total sugar content,organic acid and water content.Therefore,the membership function method is an effective way to evaluate the quality of watermelon.3、In order to predict the role of sucrose invertase gene family in sucrose metabolism in watermelon fruit this study was carried out.This study used bioinformatics methods to search and identify all the sucrose invertase gene family members of watermelon,and analyzed it.The results showed that the watermelon sucrose invertase gene family includes a total of 12 genes.Phylogenetic analysis segregated the putative sucrose invertase into three distinctively known sub-groups,of which CWINV has 5,VINV has 2 and CINV has 5,and they are all distributed on 6 chromosomes.Cell wall sucrose invertase and vacuolar sucrose invertase belong to acid sucrose invertase,cytoplasmic sucrose invertase belongs to neutral/alkaline sucrose invertase,and the two types of conservative motifs are different.Motif 1,motif 7 is highly conserved among all acid sucrose invertase proteins.The conservation of neutral/alkaline sucrose invertase protein is higher than that of acid sucrose invertase protein.Almost all neutral/alkaline sucrose invertase proteins contain 6 conserved motifs: motif 2,motif 3,motif 4,motif 5,motif 9,and motif 10.The gene structure suggests that some acid sucrose invertases have exon loss.There is a variety of cis-regulatory elements in the upstream sequence of the watermelon sucrose invertase gene family,including four categories: light response,hormone response,abiotic stress response,and developmental regulation.According to the results of quantitativeanalysis,it is speculated that Cl CWINV1,Cl CWINV2,Cl CWINV5,Cl CINV1,Cl CINV3,Cl CINV4,Cl CINV5 are involved in sucrose metabolism in watermelon.The results of this study serves as a theoretical basis for further elucidating how members of the sucrose invertase gene family regulate sucrose metabolism in watermelon fruit.