Screening Of Watermelon And Melon Rootstock Resources Resistant To Meloidogyne Incognita And Transcriptomic Analysis

In recent years, with the area of greenhouse cultivation constantly expanding and successive cultivation, the yield and economic losses of watermelon and melon increased for root knot nematode infection. The present study showed that watermelon and melon cultivars were all not resistant to root knot nematodes. So screening of nematode-resistant germplasm and rootstocks, has become one of the feasible and environmental ways to control and prevent nematodes. Until now, all of the resistant germplasm coming from the gourd family are wild materials, the molecular mechanism of its resistance is known less. In this study, the optimal inoculation concentration for the test was determined, firstly. Then, we evaluated seventy-nine accessions of Cucurbitaceae crops that can be used as watermelon and melon rootstocks by artificial inoculation. The Cucumis metuliferus was test and exhibited resistance. We got the whole genome expression profile of the Cucumis metuliferus on an Illumina Hi Seq2500 platform to analysis of the resistance to southern root knot nematode and we explored the primary molecular mechanism of Cucumis metuliferus resistant to southern root knot nematode. we got some high expression differential genes correlated with the resistance to southern root knot nematode. Main research results are as follows:1.Through the screening test for the suitable number of inoculation, determined the best number of inoculation should be 2000 J Per plant, and above 25 degrees Celsius, the temperature condition is not the key factor that affects the incidence of the disease. This test provided a reference for the subsequent identification of germplasm resources resistance.2.Among of the 32 accessions of pumpkin, besides the six accessions ‘pot shaped pumpkin’, ‘red Diaogua’, ‘Dushan long vine melon’, ‘Eighteen channel ’, ‘round pumpkin’ and ‘tin pumpkin’ showed high susceptibility, the remaining twenty-six accessions were all susceptible. We did not find the resistant germplasms in pumpkins. We found only three germplasms(‘white squash’, ‘chestnut’,‘green jade melon’) of susceptibile to southern root knot nematode in twenty winter squash and the rest are all high susceptibility. Among watermelon Germplasms, ’PI 606135’ ’PI 482298’ ’PI 189225’ ’PI 482324’ showed moderate resistance, the ’PI 189225’ ’PI 482324’ were consistant with the previous research results and the ’PI 606135’ ’PI 482298’ were newly discovered resistance germplasms, the remaining nineteen accessions were susceptible to southern root knot nematode. 4 wild relatives of melon germplasm, the Cucumis metuliferus showed resistance, C. metuliferus var and C. anguria were moderate resistance, C. ficifolius was susceptible. By the identification of 79 germplasm, 1 of them showed resistant and 6 of them were moderate resistant. Through the 4 species of the Cucurbitaceae germplasm of different materials identification, the four germplasm materials of the average grade of disease index from small to large, followed by wild relatives of melon, watermelon, pumpkin, winter squash.3 By transcriptome sequencing, we obtained 116.03 Gb Clean Data, Clean Data of all samples reached 6.16 Gb, the percentage of Q30 bases was 91.27% or above. We assembled a total number of 93795 Unigenes. There were 19263 Unigenes over length of one KB. By blast with NR, Swiss-Prot, KEGG, COG, KOG, GO and Pfam database, we obtained 54583 Unigene annotation results. Based on differential gene expression patterns in different samples, we did Pattern clustering, functional annotation and enrichment analysis.Results show that the differential expression genes were mainly related to hormones, plant defense response, transcription factors and cell formation. Based on the enrichment analysis, we found the main differentially expressed genes were enriched in plant hormone signal transduction, plant pathogen interactions and phenylpropanoid biosynthesis and Phenylalanine Metabolism and other metabolic pathways. High expression of differential genes most were pathogenesis related proteins and AP2, MYB, WRKY transcription factor. After inoculation, The DEGs of four samples involved plant hormone signal transduction related were most. The AP2 transcription factor and the resistance gene of Cucumis metuliferus to southern root knot nematode are closely related. Jasmonic acid metabolism, phenylpropanoid biosynthesis, Phenylalanine Metabolism and other metabolic pathways may participated in the interaction reaction between Cucumis metuliferus and southern root knot nematode. The results show that nematode infection induced the plant complex defense responses.