Genetic Mapping And Transcriptome Analysis Of Gummy Stem Blight Resistance In Melon PI420145

Gummy stem blight（GSB）is one of the main diseases threatening the quality production of melon（Cucumis melo L.）,which can occur in the whole growth period.It is the most economical and effective method to select resistant varieties by using resistant germplasm resources.The melon resource PI420145 has high resistance to Didymella bryoniae,and it is of great significance to explore resistance genes and closely linked molecular markers of PI420145 to resistance to GSB.In addition,as the first step of gene expression,transcriptome analysis is an important means to study phenotype and gene function.Therefore,in this study,PI420145 was selected as the research object,through molecular marker genetic map was constructed,the candidate genes were screened and analyzed,and the differential expression of m RNA/lnc RNA before and after inoculation was analyzed to explore the resistance mechanism.The main research is as follows:1.Mapping of resistance gene to GSB of PI420145In this experiment,the inbred lines of the resistance source PI420145 and the susceptible cultivar’Baipicui’of melon were used as parents to construct F₁.The F₂ temporary population was obtained after self-pollination,and the phenotype of the population at seedling stage was analyzed.A genetic map was constructed using molecular markers,the resistance gene of PI420145 was located between 4.29-4.64 Mb on chromosome 10.According to the reference genome,the coding proteins,expression levels of 49 genes in 344.58kb region were analyzed.,MELO3C011814.2,MELO3C011827.2,MELO3C011836.2,MELO3C011839.2,MELO3C011852.2,MELO3C011856.2,MELO3C011859.2 and MELO3C011865.2 were selected as candidate genes for resistance to PI420145.2.Transcriptome analysis of melon resistance to GSBIn order to explore the role of lnc RNA in melon resistance to D.bryoniae,the resistance inbred line PI420145（A）and the susceptible inbred line’Baipicui’（B）were used as the research objects in this experiment.RNA-seq was performed before and after inoculation（0d and 2d）.The results showed that 1.088 billion clean reads were filtered from 12 libraries,and 19026 m RNA and 974 lnc RNA were screened.Compared with the control,the number of PI420145 transcripts decreased,but the number of down-regulated m RNA and lnc RNA increased.The results showed that 4327 m RNA and 64 lnc RNA were differentially expressed in A2vs A0,7372 m RNA and 160 lnc RNA in B2vs B0,respectively.Gene function analysis indicated that there were more Gene Ontology terms and pathway related to disease resistance in PI420145,including protein phosphorylation,cell wall organization or biogenesis,diterpenoid biosynthesis and plant-pathogen interaction;while in’Baipicui’,there were more genes and lnc RNA related to cell process,proton-transporting ATP synthase complex,carbolic metabolism and autophagy.The prediction results of m RNA-lnc RNA pairs of candidate gene showed that,MELO3C0011814.2.1-LNC＿000859、MELO3C011827.2.1-LNC＿000859 and MELO3C011852.2.1-LNC＿000570 may be involved in the resistance process of PI420145.These results indicated that PI420145 activated more resistance related genes and pathways to resist the pathogen infection,and lnc RNA was involved in the defense response of melon to the pathogen infection.In this paper,lnc RNA involved in the resistance of melon PI420145 to GSB,which laid a foundation for elucidating the molecular mechanism of non-coding RNA in melon resistance to GSB.