QTL Analysis Of Resistance Against Meloidogyne Incognita And Identification Of CsMYB Gene Family In Sativus-hystrix Introgression Line IL10-1

Cucumber（Cucumis sativus L.）is an annual herbaceous plant which belongs to the Cucumis genus of Cucurbitaceace.It is widely loved by consumers because of its rich nutrition,unique taste,and diverse eating methods.However,cucumber is easily affected by powdery mildew,downy mildew,vine blight,fusarium wilt and other diseases,as well as RKN,aphids,thrips and other pests.Among them,M.incognita is the main RKN population that causes serious damage to cucumber roots,which can lead to the decline of cucumber yield and quality.Up to now,no cucumber cultivars against to M.incognita have been reported.In addition,the cucumber genetic basis is narrow,so it is difficult to obtain new cultivars through traditional hybridization.Then,the interspecific introgression line material obtained through interspecific hybridization has become an important way to select cucumbers against to RKN,and it is important for the utilization of antagonistic genes to study and explore its resistance mechanism in cucumber.Therefore,it is important to mine the genes of against M.incognita in the introgression line material IL10-1 and analyze the gene family that can regulate the Hub gene.In this study,the RIL population,which were constructed with the resistance material IL10-1 and the susceptible material CC3,was inoculated with M.incognita to identify RKI,and the RIL population materials were used to build S＿pool,sequencing and analysis with Mutmap method to obtain the QTL of the resistance gene.At the same time,previous transcriptome studies found that LTP gene is the Hub regulatory gene against M.incognita in cucumber.The gene family analysis of MYB gene,which can regulate Hub gene LTP,was carried out to further illustrate the effect of MYB resistance to M.incognita in cucumber.The main findings are as follows:1.QTL Analysis of Resistance to M.incognita in sativus-hystrix introgression line IL10-1.In order to screen and identify resistance candidate genes against Meloidogyne incognita in cucumber,123 recombinant inbred line materials F_2:6,which constructed by the resistance sativus-hystrix introgression line IL10-1 and the susceptible material Beijing Jietou CC3,were artificially inoculated Meloidogyne incognita and counted the RKI.Then,the seriously susceptible materials sampled alone to establish the S＿Pool for sequencing analysis.The mutation sites related to resistance were determined by SNP-index analysis.Meanwhile,the sativus-hystrix cucumber introgression line IL10-1 was sequenced and compared with Chinese Long 9930＿v3.The results showed that RKI distribution of the RIL population of IL10-1 satisfies the normal distribution model.With Mutmap analysis,the candidate interval QTL was located in the seven intervals of 5 chromosomes,a total of 17.7 Mb,respectively0.3 Mb on chromosome 2,1.8 Mb on chromosome 2,0.5 Mb on chromosome 3,3.7 Mb on chromosome 3,3.7 Mb on chromosome 5,1.9Mb on chromosome 6,5.8 Mb on chromosome7.2.Identification and analysis of CsMYBs gene family in cucumberPlant MYB transcription factors play an important role in plant physiological metabolism and biotic and abiotic stress.Previous studies have found that MYB transcription factors may be involved in the regulation of the hub gene LTP in introgression lines IL10-1against M.incognita.The systematic analysis of cucumber CsMYB gene family were carried out.All the sequences of cucumber CsMYBs gene family were established by hidden markov model（HMM）and CDD and SMART database,and the chromosome location,conserved motif,gene structure,evolutionary tree,cis-acting element of promoter region,evolutionary relationship with Arabidopsis thaliana and expression of the obtained gene family were carried out.The results showed that cucumber contained 112 CsMYBs genes.Based on the analysis of evolutionary tree,gene structure and conservative motif of 112 proteins,it is found that most of the genes could not be grouped together,and it was speculated that there might be repetition or loss in the process of evolution in order to adapt to the new environment,followed by specific evolution.Gene replication analysis showed that the amplification of CsMYBs gene family depended on tandem repeat events rather than fragment repeat events.The analysis of the expression of CsMYBs in different tissues and organs showed that the gene family had specific expression.QRT-PCR analysis showed that there was differential expression of MYB gene between R-line and S-line,and the expression trend of Csa1G021940、Csa5G641610 and LTP genes was relatively consistent.