Genetic Analysis And Molecular Regulation Of Parthenocarpy In South China Type Monoecious Cucumber

Cucumber(Cucumis sativus L.)is one of the vegetable crops with important economic value.The fruits of most cucumber lines depend largely on pollination,especially in greenhouse,if the environment is not good for pollination,the fruit yield of will be greatly affected.Parthenocarpic crops can bear fruit without pollination and improve the quality of fruit.The predecessors researched on parthenocarpy of cucumber mainly in foreign liness.The Monoecious cucumber with parthenocarpy can ensure the fruit yield no matter pollination or unpollination,and we choose Southern China Ecotype cucumber which is a native cucumber and an excellent germplasm resources to explore the genetic model and regulation mechanism of Parthenocarpy.In this experiment,Southern China monoecious extreme materials which are parthenocarpic or nonparthenocarpic were selected to cross to be a hybrid combination,and the genetic analysis,QTL mapping and transcriptome sequencing were carried out for parthenocarpy.The results are as follows:(1)The strong parthenocarpy material "RH" of the South China-type monoecious cucumber and the weak parthenocarpy material "Cuiqiu" of the South China-type cucumber as the parental lines to get the 4th generation hybrid combination,then the genetic regulation will be analysed by using major genes and multiple genes Analyze the model.The results showed that the parthenocarpy rate of F2 population in autumn 2018 and spring 2019 showed normal distribution,which was in line with the genetic regulation of quantitative characters;the parthenocarpic rate of South China type monoecious cucumber was in line with MX2-AD-AD genetic model controlled by two major genes+polygenes,and the major genes and polygenes genetic rate were 80.16%an 0%,The two major pairs of genes are dominated by additive effects.(2)Use the experimental materials "RH" and "Cuiqiu" as parents to construct the F2 segregation group.The 25 extremely strong parthenocarpic materials and 25 extremely weak non-parthenocarpic materials are selected in F2 were used to construct a mixing pool for QTL-seq.We found a QTL locus parth5,located in the front region of chromosome 13,200,00020,000,000 bp on Chr5.This region is 6.3 Mb and contains a total of 48 genes.(3)Using Near isogenic lines of South China type cucumber,strong Parthenocarpic material "K31" and non-parthenocarpic material "K33" as experimental materials,the fruits of 3 different periods(d0,d2,d4)which are unpollination were conducted transcriptome sequencing.The results showed that "K31" had 1471 DEGs in 3 periods(d0,d2,d4),of which 765 were up-regulated and 706 were down-regulated.In the "K33",there were 11,233 DEGs in the three periods,of which 5,153 were up-regulated and 6,80 were down-regulated.The number of genes involved in parthenogenesis is less than the process of abortion of non-parthenocarpic fruit.(4)The results based on Go enrichment and KEGG pathway analysis,the differentially expressed genes in the fruits of strong parthenocarpic and non-parthenocarpic materials of cucumber were mainly related to the biosynthesis,metabolic pathway,protein binding,ATP binding,nucleotide binding,DNA binding,ion binding and transport,cell membrane components,cell and biological regulation,oxidoreductase activity,etc Access.Combined with the QTL sequencing results,we predicted 17 genes that may be involved in the formation and regulation of Parthenocarpy at parth5 locus.This study can make a foundation for the study of parthenocarpic genes and the breeding of South China type monoecious and strong parthenocarpic varieties.