| Sweetpotato is a corp with homologous hexaploid(2n=6x=90)with some heterologous sources.Sweetpotato show highly heterozygous genotypes,complex genetic background,and self-incompatibility and incompatibility between varieties within the same infertility group.The larg number of chromosomes are unstable in sweetpotato.It is one of the most difficult crops in genetic studies such as map construction and QTL mapping.In this study,we collected 75 sweetpotato varieties in China.The fingerprints of 75 sweetpotato germplasms were constructed by SSR molecular marker.Meanwhile,the genetic diverisity was analysised by agronomic morphological markers and SSR molecular marker,aiming to provide a theoretical basis for the identification and phylogenetic analysis of sweetpotato germplasms.It will be a useful reference for the selection of the parental parents in sweetpotato hybridization breedingpragrams.The main results are as follows:1.Theagronomic traits of 75 sweetpotato germplasms materials were investigated in this paper,such as the leaf shape,top leaf color,the color of the potato peel,the color of the potato,the length of the longest branch,the number of branches at the base,the stem diameter,dry rate and the tuber yield.The average variation coefficient of different characters of sweetpotato varieties was from 27.64%to 69.33%,showing that themorphological diversity of sweetpotatos was relatively abundant.2.In this study,the genetic diversity of 75 sweetpotato varieties was analyzed by using agronomic traits.and the DPS3.01 statistical software was used to calculate the genetic distance among the varieties.The data showed that the genetic distance between 75 sweetpotato varieties was 2.2361?12.6491,with an average of 6.7878.These results indicated that the genetic diversity of the varieties was abundant.At GD=7.13,the 75 sweetpotatos could be divided into four categories by unweighted pair-group method with arithmetic means(UPGMA):Class ?,?,?,and ?.At GD=5.06,Class I could be divided into 4 subcategories:I-1,I-2,I-3 and I-4;Class ?could be divided into 2 subcategories:?-1 and ?-2.Agronomic traits of similar varieties were clustered into onecatagory.3.In order to screen polymorphic primers,PCR amplification was carried out using the genomic DNAs of sweetpotato cultivars fu Y6-7 and Wanshu 8 as templates,and 19 pairs of primers were selected from 90 pairs of SSR primers.The selected 19 pairs of primers were used for polymorphism analysis of 75 sweetpotato.The results showed that the average polymorphic information content(PIC)revealed by these primers was 0.8149 and the range of variation was 0.6757-0.9317.Meanwhile,232 alleles were amplified by 19 pairs of primers,12.21 alleles were amplified per pair of primers on average;A total of 165 polymorphic sites were amplified,4?18 per pair of primers,with an average of 8.68,and the polymorphism ratio was 71.1%.The results showed that the 75 sweetpotato varieties showed rich diverisity in 19 pairs of primers,indicating that the primers selected in this study can distinguish each varieties well,and these can be used for the identification of sweetpotato germplasm.4.In this study,the amplified bands were read manually.The presence or absence of each polymorphic sites was indicated by "1" or "0",the amplified bands of 19 pairs of primers were statistically analyzed and genetic distances(GD)among 75 sweetpotatos were calculated by NTSYS-pc 2.10 software.The results showed that the genetic distances between sweetpotato varieties were from 0.0455 to 0.7333,with an average of 0.4646.The tested materials were relatively abundant based on gengtice distance analysis.The UPGMA cluster map grouped these 75 sweetpotato varieties into six categories:Class ?,?,?,?,?,and ?.Class ? contains 63 sweetpotato varieties,which could be divided into 17 subcategories.5.Considering the PIC value,genotype number,and number of alleles of primers,two pairs of primers with good polymorphism were selected from the 19 pairs of SSR primers:primer SSR9 and primer C33.The PIC value of the primers is greater than 0.9.The number of alleles of primer SSR9 polymorphism was 18,and the genotype number 74.The number of polymorphic sites of primer C33 was 14,and the genotype number was 52.According to thesequential order of primers SSR9 and C33,the alleles wereassigned as "0" "1" to construct digital fingerprints of the 75 sweetpotato cultivars.The digital fingerprints could be used distinguish the sweetpotato germplasms.6.The correlation between agronomic traits and SSR marker revealed genetic distance of the studied sweetpotato was carried out and the correlation coefficient r=0.0326.This results indicated that the correlation between the genetic distance generated by the two methods is not significant.The clustering analysis result showed that the sweetpotato whith the same or similar arronomic traits were distributed in different branches generated by SSR clustering. |
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