Analysis On Melon Genetic Diversity And The Effect Of Potassium On The Quality Of Different Melon Genotypes

Melon is one of the main horticultural crops of Cucurbitaceae.In recent years,with the improvement of living standards, people put forward higher request on melons’ quality.In this research, we colleted59melon materials,used morphological markers and SSR molecular markers analysised the population genetic diversity and phylogenetic relationship of the materials.On this basis,we selected two varieties "Flavor4" and "Xuelihong".Under the different potassium treatments,analysing the the influence of potassium on melon quality and the gene expression of fruit suger and acid accumulation related enzymes to establish the suitable applying potassium contents,and investigate the regulation of potassium on the melon quality. This study obtained the following results:1.Using morphological markers and SSR molecular marker identified the germplasm resources of59melon materials. Select11agronomic traits for morphological marker analysis;a total of46pairs of EST-SSR primers were selected for the molecular marker analysis,among them,23pairs of primers amplified polymorphism bands. In59melon genotypes, the average PIC value detected by23EST-SSR markers is0.386.The results of genetic analysis showed thatmorphological markers put all the materials into4groups in2types, there are some differences between the traditional methods to distinguish melon with thick and thin-skinned. SSR molecular markers clustered all the materials into two types of thin-skin and thick-skin obviously,and thick-skin types can also be divided into classes of net or smooth peel and yellow or white peel.But in the same type,the genetic similarity coefficient is relatively large, showed the narrow genetic background, and the little difference in the materials.2.0n the basis of genetic diversity analyzing,we selected melon varieties "Flavor4" and "Xuelihong" as materials, which have the better characters and larger genetic differences. With different gradients of potassium supplements(nutrient solution K2SO4concentration of0,117,234and351mg/L), measured their appearance and intrinsic nutrition indicators.The results showed that under the moderate concentrations (nutrient solution K2SO4concentration of117mg/L and234mg/L)of potassium treatment,the major economic traits such as soluble solid,sucrose, and flavor compounds are better than the low potassium and high potassium treatments, so made the better performance on fruit quality. 3.Using the technology of real-time PCR, we measured the relative gene expression of the sugar and acid related enzyme in two varieties.Results showed that under the moderate potassium treatment,the expression levels of sucrose synthesis related enzymes (sucrose phosphate synthase and sucrose synthase)was lower than the rest of the processing.Moreover, in the moderate potassium treatments,the expression levels of sucrose degradation related enzymes(acid invertase and neutral invertase)of "Xuelihong" was significantly higher than the rest of the processing and the "flavor4" of all the processing.At the same time,the gene expression in citric acid metabolic enzymes did not consistently show that the fruit under medium concentration potassium treatments have more accumulation.But in this study,the results of sugar and acid contents showed:under the medium concentration potassium treatments,fruit sugar and citric acid contents were significantly higher than that of low potassium and high potassium treatments.So we can guess, the varieties for this experiment may have the unique sugar and acid accumulation pathway,and the accumulation process may have some post-transcriptional regulation or the co-regulation of the enzymes.The results of the study suggests that the genetic background of59melon varieties is relatively narrow,most of them are thick-skin melon.We should expand the selection range in the breeding process,and exploit melon genetic resources effectively based on the melon germplasm genetic relationship this paper revealed.In addition,suitable potassium supplement can make important effect on the improvement of melon quality,we should going further to explore the mechanism of potassium’s influence on the quality of melon,and perfect melon efficient cultivation system from more aspects.