| Cucumis melon(2n=2X=24)is one of the top ten fruits in the world,and its planting area is extensive in China.As early as the Sheng Nong's herbal classic there is a record of "melon pedicle is the top grade medicinal herbs," its cultivation history has been more than a thousand years ago.The origins of melons in the world are widely distributed and have rich genetic diversity.However,due to the lack of cross-breeding barriers between different germplasm types,combined with long-term artificial domestication and selective orientation,the variation of melon breeding materials has become increasingly monotonous,and its breeding work has progressed.Slower.In order to effectively use the melon germplasm resources and break through the resource bottleneck of melon breeding,it is necessary to carry out extensive and continuous collection and research of various melon germplasm resources.The research group has been devoted to the collection and utilization of melon germplasm resources.Nearly a thousand germplasm resources including thick bark,thin bark,and wild melon have been collected,but the genetic relationship between different types of germplasm is not Completely clear.This study selected 191 representative germplasms from existing germplasm resources,including 62 striffen muskmelon germplasm,89 muskmelon germplasm,and 40 wild-type germplasms.Many morphological traits were counted for many years.Combined with SSR markers,the diversity and genetic relationship of these three germplasms were evaluated.The results are as follows:1.Genetic diversity parameters of morphological traits: Shannon diversity index of all germplasms varied from 0.34 to 2.47 with an average of 1.38.The variation of 13 quality trait diversity indices was from 0.34 to 2.47.For 1.18,the diversity index of five quantitative traits varied from 1.53 to 2.07,with an average of 1.90.The diversity index of quantitative traits was generally higher than that of quality traits,indicating that the diversity of quantitative traits of melon germplasm was more abundant.The average diversity index of muskmelon was 1.31.The variation of the four characteristics of fruit surface color,melon pod color,melon pod moisture,and fruit quality was significant.The mean diversity index of muskmelon was 1.38.The fruit shape,fruit surface netting,and net The variation of six characters,such as pattern distribution,reticulate density,reticulate roughness and flesh fragrance,was obvious.The average diversity index of wild melon was 1.39.The average diversity index of the three types of melon germplasm has little difference.2.The principal component analysis shows that 18 morphological traits can be synthesized into 5 principal components,and the cumulative contribution rate is 82.297%,indicating that the 5 principal components can represent most of the phenotypic information of the whole melon population.The first principal component is related to fruit surface texture,reticulate texture,reticulate density and reticulate roughness,the second principal component is related to the color of the coating and the shape of the coating,the third principal component and the middle fruit shape and the color of the melon Relevantly,the fourth principal component is related to flesh flesh color and pulp flavour,and the fifth principal component is related to fruit ground color and fruit flesh thickness.3.Cluster analysis of morphological characters classified all melon germplasms into seven groups(I,II,III,IV,V,VI,VII).The morphological traits of melon germplasm in different groups have certain differences..Group I has a total of 3 accessions,all of which are meloned germplasm.The fruit length in this group is as large as 100 cm.The fruit shape is sticky and the fruit surface is white.The flesh of the group has a relatively low sugar content.There were a total of 6 germplasms in group II.There were obvious reticulate distributions in this group,with orange or orange-red flesh.Group III has a total of 7 accessions,including 5 thick skins,1 thin skin,and 1 wild,white pulp,white guaran,no scent,and hard meat.There were a total of 30 germplasms in group IV,including 24 muskmelon germplasms and 6 striffen muskmelon germplasms.The group had obvious reticulate textures,green striated lines,and a thick flesh with an average of 3.12 cm.There were 9 germplasms in the group V,including 4 muskmelon germplasms,3 striffen muskmelon germplasms,and 2 wild germplasms.The fruit shape of this group was rod-shaped,green or yellow fruit surface,without netting and overprinting.There were 61 germplasms in the group VI,including 30 striffen muskmelon germplasms and 31 wild germplasms.The characters were no reticulate patterns,the overprinting patterns were heavy,and the fruit weight was small,with an average of 0.252 kg Group VII contained 76 materials,including 56 striffen muskmelon germplasms,24 melo germplasms,and two wild germplasms.The major traits were mostly no reticulate lines,paler fruit background,and mostly white.4.36 SSR markers detected 314 polymorphic loci in all germplasms,with an average of 8.72 markers per marker,with an average effective allele number(Ne)of 3.99;Shannon index(Shannon information index I)at each site The range of variation was 0.95 to 2.22 with an average of 1.58;the average expected heterozygosity(He)was 0.74,and the amplitude was between 0.48 and 0.87.The trends of both the I index and the He value are basically the same.The polymorphic information content(PIC)ranged from 0.45 to 0.86 with an average of 0.69.The total number of alleles(Na)in thin-leaf germplasm was 256,with an average of 7.11,and the I value ranged from 0.51 to 2.00 with an average of 1.29.The PIC values varied from 0.23-0.81 with an average value of 0.57.The total number of alleles(Na)of melon germplasm was 226,with an average of 6.28,the I value varied from 0.45 to 1.84,with an average of 1.30,and the PIC value varied from 0.22-0.79 with an average value of 0.60.The total number of alleles(Na)in the wild germplasm was 250,with an average of 7.14,and the I value ranged from 0.64 to 2.47 with an average of 1.55.The PIC value ranged from 0.26 to 0.88 with an average value of 0.69.The specific molecular markers for striffen muskmelon,melon,and wild germplasm were 10,8,and 10,respectively.Comparative analysis showed that among the three types of germplasm,the average I and PIC values of the wild germplasm were the highest,Na was comparable to that of the striffen muskmelon germplasm,but it was significantly higher than that of the muskmelon germplasm,indicating that the wild germplasm diversity is more diverse and contains More rare genes.5.Cluster analysis based on molecular markers showed that all germplasms were divided into 4 categories(I,II,III,and IV),and M344 and M343 were clustered into a single species,all of which were thin Pipi germplasm;Materials,including 15 parts of thin skin material,33 parts of wild material and 2 parts of thick skin material;54 species of material in category III,including 3 parts of thin skin germplasm,50 parts of thick skin material,1 part of wild species;85 parts of group IV Germplasm,including 69 striffen muskmelon germplasms,10 muskmelon germplasms and 6 wild germplasms.The result of molecular marker clustering was basically the same as the germplasm type,but it was significantly different from the phenotypic clustering,which may be due to the gene exchange between different germplasms.6.The genetic distance and differentiation coefficient calculation results of different germplasms showed that the Fst between the striffen muskmelon germplasm and the muskmelon germplasm was the highest,which was 0.102,and the genetic distance GD was 0.380,indicating a moderate degree of genetic differentiation between the two;Between the wild and the germplasm,the Fst was 0.100;the differentiation of the bark and wild germplasm was the lowest,and the Fst was 0.083.This result shows that the genetic differentiation among melon germplasm mainly manifests in the differentiation among subspecies,namely the differentiation between agrestis type and melo type. |
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