Excavation Of Flavor Nutrients And Screening Of Excellent Germplasm Resources Of Wax Gourd

Wax gourd（Benincasa hispida）is popular as a kind of medicinal and edible vegetable,which is deeply loved by consumers because of its unique flavor and rich nutrition.With the improvement of people’s living standards,quality determines consumers’choice of vegetable products.Rich nutrition and good flavor have become the main objectives of vegetable breeding.Therefore,it is an urgent need for industrial development to carry out the research on the flavor and nutrition of wax gourd.However,at present,the main flavor and nutrition of wax gourd are not clear,which restricts the process of quality breeding of wax gourd.Based on this,the flavor and nutrition of wax gourd germplasm resources were evaluated and analyzed,and the key genes regulating the formation of flavor and nutritional quality of wax gourd were preliminarily discovered by multi-omics.,finallythe effects on wax gourd fruit quality of different plant hormones were analysed.To sum up,the results provide theoretical and material basis for genetic improvement of wax gourd quality.The main results are as follows:1.The flavor and nutritional quality of wax gourd are quite different among different germplasm resources.The flavor nutrients such as sugar and acid were measured on 112inbred lines of wax gourd from home and abroad,and it was found that fructose and glucose were the most important sugars in wax gourd fruit,the fructose content was between 113.52-210.45 mg/g DW,and the glucose content was between 79.48-79.48mg/g DW.Between 235.72 mg/g DW;the main organic acid in wax gourd fruit is malic acid,and its content is between 12.78-65.54 mg/g DW;wax gourd is rich in citrulline and ascorbic acid,and the content of citrulline is 5.60-23.41 mg/g DW,the ascorbic acid content is between 0.5-4.23 mg/g DW.In this study,it was found that the main components affecting the flavor and nutritional quality of wax gourd were:fructose,malic acid,citrulline and ascorbic acid.On this basis,a number of high-quality germplasm resources were screened.2.The accumulation of soluble sugar,organic acid,citrulline and ascorbic acid during the development of wax gourd fruit was studied.It was found that the contents of fructose,glucose and citrulline accumulated gradually with the development of fruit,while sucrose,shikimic acid and fumaric acid decreased gradually with the development of fruit.The accumulation rule of malic acid and citric acid was the same,and the content of ascorbic acid decreased at first and then increased.The content of ascorbic acid decreased gradually with the development of fruit.3.Based on the study of transcriptome and metabolic group,the key genes of flavor nutrition were excavated from two aspects（the same variety at different developmental stages and different varieties at the same developmental stage）.It was found that the expression of alkalineα-galactosidase coding gene Bhi03G001926 was significantly positively correlated with fructose and glucose accumulation.The expression of malate dehydrogenase coding genes Bhi12G001426 and Bhi01G000427,phosphoenolpyruvate carboxylase gene Bhi12G000721 and Bhi09G002867 were positively correlated with malate accumulation,while the expression of arginine succinate synthase gene Bhi02G000401 was negatively correlated with citrulline accumulation.To sum up,Bhi03G001926 is an important gene regulating fructose accumulation,Bhi12G001426,Bhi01G000427,Bhi12G000721 and Bhi09G002867 are important genes regulating malic acid accumulation,and Bhi02G000401 is an important gene regulating citrulline accumulation.4.The effects of plant hormones on the flavor and nutritional quality of wax gourd fruit and the gene expression of related metabolic enzymes were studied.It was found that exogenous GA₃treatment significantly increased the content of fructose in wax gourd fruit,while exogenous GA₃,ABA and 6BA significantly decreased the content of ascorbic acid.The genes with high response to plant hormones were screened and verified by q RT-PCR method.It was found that the expression of alkalineα-galactosidase gene Bhi03G001926 and Bhi09G002818,acid invertase gene Bhi09G002576 and sucrose synthase gene Bhi08G001620 were positively correlated with the change of fructose content induced by GA₃,while the expression of sucrose synthase gene Bhi11G001031was negatively correlated with the change of fructose content induced by GA₃.The expression of Bhi03G001129,the key gene of ascorbic acid synthesis pathway in wax gourd,was positively correlated with the content of ascorbic acid.To sum up,GA₃regulates the accumulation of fructose by affecting Bhi03G001926,Bhi09G002818,Bhi09G002576 and Bhi08G001620,while GA₃,ABA and 6BA regulate the accumulation of ascorbic acid by affecting Bhi01G001485.