| Melon(Cucumis melo L.)is an annual herb of the Cucurbitaceae family with a wide range of genetic diversity and phenotypic diversity.China is one of the earliest countries to cultivate melons in the world,and it is also the country with the largest melon cultivation area and the highest yield.Different from the long internode varieties,the short internode melon has the advantages of compact plant type,no pruning,ventilation and light transmission,and is suitable for simple cover facility cultivation and mechanized harvesting,and can also increase planting density and save under various cultivation conditions.Therefore,short internode trait is often used as key traits for ideal plant types in breeding,and more attention has been given to breeders.In this study,the short internode melon M406 and long internode melon M323 were used for genetic map constructin and gene mapping.The genetic regularity of the short internode M406 trait was clarified,and the short internode(si)was fine mapped.The result will be very helpful to explore the molecular mechanism of the formation of short internode and its regulatory networks.The main findings are as follows:1.The inheritance analysis of short internode trait in melon After 45 days of planting,the plant heights of M406,M323,F1,and F2 populations were determined.The phenotyping results showed that the ratio of long internodes and short internodes in the F2 population was 3:1(χ2=0.8588<χ20.05=3.84),indicating that the short internode trait was controlled by a pair of recessive genes,which was named short internode(si).2.Map construction and segregation distortion analysis of melon genetic map Using the parents M323 and M406 to screen the polymorphisms of the 1,205 SSR primers devekoped in our group.411 SSR primers with polymorphism between the parents were obtained,and the polymorphism rate was 34.11%.A total of 92 F2 individuals were analyzed using 353 polymorphic primers to construct a genetic map.The map contains 353 SSR markers and a short trait phenotypic marker,12 linkage groups covering a total length of 1565.49 c M with an average distance between markers is 4.42 c M,and the linkage length was ranged from 86.98 c M to 186.68 c M.Through χ2 test of 353 SSR marker genotypes,it was found that 34 molecular markers showed segregation distortion at the 0.05 level,accounting for 9.63% of the total markers.Among these markers,16 were extremely significant,locating on the linkage groups LGII,LGIII,LGIV,LGV,LGVI,and LGVII,accounting for 47.06% of the total segregation distortions markers.4.Fine mapping of short-internode(si)gene in melon.On the basis of the preliminary mapping,This study selected 65 pairs of SSR primers in the candidate segment.In addition,This study performed genome re-sequencing of the parental line M323 and M406,14 pairs of Indel primers were developed based on sequence compariso.4 pairs of SSR markers and 7 pairs of Indel markers with clear band and large differences were finally selectd for fine mapping.The si gene was further mapped between Indel14 and Indel3 with genetic distances of 1.4 c M and 0.3 c M,respectively.In this candidate segment,based on the SNP difference between the two parents,This study developed 4 pairs of d CAPS markers.Finally,the si gene was mapped between the markers d CAPS1 and d CAPS4 with a physical distance of 110 kb.The melon genome annotation,12 ORF were found.According to two heavy sequencing of the comparison results show that the parents in a total of 2 SNP candidate sections one located in gene spacer,another is located in MELO3C016916 exons,According to the d CAPS2 marker designed by the SNP loci,the genotype analysis of the recombinant single strain showed that d CAPS2 and si gene expression were co-segregation,indicating that the gene was the candidate gene for controlling the short-internode traits.The gene encoding LRR receptor-like serine/threonine-protein kinase ERECTA isoform X1,or ERECTA gene,was shown by BLAST comparison. |
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