Genetic Analysis Of Rind Stripe And Fine Mapping Of The Determinate Gene In Melon (Cucumis Melo L.)

Melon(Cucumis melo L.)is one of an important economic fruit crops with sweet taste and freshness,which belongs to angiospermae、dicotyledoneae、cucurbitaceae and cucumis,named by the special flavor and higher sugar content.According to the statistics of FAO,the production of melon has averaged more than 29 million tons over the past 10 years.Melon is grown in temperate and tropical countries.The main production areas in Asia,and the United States and Spain followed suit.The cultivation area and the output of chinese melon rank the number one all over world.With the increasing demands of market consumers on the quality and appearance of melon,the research on the phenotypic characters of melon has been highly valued by researchers at home and abroad.Therefore,it is possible to provide theoretical basis for the breeding of melon rind by identifying the genetic law of rind stripe and digging out the regulatory gene.In this experiment,we obtained an F2 melon population derived from self-crossing an F1 generation from a cross between X010(green rind with stripes)and M1-113(white rind without stripes)and performed genetic analysis and mapping.They were planted in xiang yang farm,a experimental base,of northeast agricultural university in 2017 and 2018.According to two years of field datas,the genetic law of melon rind stripes was determined.Subsequently,in the F2 generation population,we selected 20 striped rind and 20 solid-colored rind plants,and extracted the DNA of them respectively.According to bulked segregant analysis(BSA),two DNA bulks were constructed(20 striped and 20 solid-colored rind plants).Next-generation sequencing(NGS)was used on two parental lines(X010 and M1-113)and two DNA bulks.According to the results of BSA-seq,CAPS markers were developed on the target chromosome,and 93 F2 individuals were used to construct genetic linkage map,and the genetic linkage map was used for QTL analysis.Subsequently,we obtained the initial mapping interval about the melon rind stripes,and CAPS markers were further developed in this interval,and used for identifying recombinants in a large 739 F2 plants,the mapping interval was further narrowed.In the end,we analyzed the candidate genes in the fine mapping range.This Experiment provides theoretical basis for molecular marker assisted breeding of melon rind stripes.The results are as follows:(1)Plants of F1 generation were all green rind with stripes.In 2017,the ratio between striped rind and non-striped rind in F2 individuals was 134:45,which was in line with the proportion of 3:1,and ?2=0.016<?20.05;In 2018,the ratio between striped rind and non-striped rind in F2 individuals was 419:131,which was in line with the proportion of 3:1,and ?2=0.016<?20.05.Therefore,the striped rind is dominant than pure color rind in melon,which is controlled by a single gene.(2)By analyzing the results of BSA-seq,the Cmst3 gene was identified on chromosome 4 within 2.7 Mbp(267,879 bp~3,025,394 bp).Fourty cleaved amplified polymorphic sequences(CAPS)markers were developed,and sixteen CAPS markers with polymorphisms on chromosome 4(the polymorphism rate was 40.0%)were used for constructing a genetic linkage map.The total length of the map was 150.26 c M,and the average distance between markers was 9.39 c M.Eventually,a locus(Cmst3)closely linked to the melon rind stripe trait was mapped between the CAPS makers M-4-1 and M-4-12.The physical distance was approximately 827 kbp and was found between 288,972 bp and 1,116,282 bp.This result was consistent with the results of the BSA sequencing analysis and further reduced the mapping distance.(3)Finally,primers were designed between the marker M-4-1 and M-4-12,and a larger F2 populations was used for identifying the recombinants.Ultimately,the Cmst3 gene was mapped between the M-4-25 and M-4-27 markers,and the physical distance was narrowed to 172.8 kbp(825,451 bp~998,292 bp).There were twenty-three candidate genes in this interval,and eight genes had non-synonymous mutations in coding region,and 11 genes also contained SNP locus in promoter region,as well as partial INDEL.