Impact of Mapped SSR Markers on the Genetic Diversity of Apricot (<Emphasis Type="Italic">Prunus armeniaca</Emphasis> L.) in Tunisia

The impact of mapped microsatellites on the study of genetic diversity of Tunisian apricot accessions was assessed. The genetic variability of 47 traditional apricot cultivars originating from several areas in Tunisia was investigated with 32 polymorphic microsatellite loci selected for their location throughout the eight linkage groups of Prunus genome. The higher polymorphism and greater transportability of these markers among Prunus species were proved by the expected heterozygosity (He = 0.56) and Shannon’s index of diversity (I = 1.05), indicating that Tunisian apricot germplasm maintained a substantial level of genetic diversity. According to their geographical origin, the genetic differentiation among groups (north, center, and south; Fst = 0.04) was lower, while the gene flow among groups was consequent (Nm = 4.79), attesting a narrow genetic background of apricot in the country. Both unweighted pair-group method with arithmetic mean dendrogram, based on Nei’s genetic distances and factorial correspondence analysis, separated northern cultivars from central and southern cultivars, revealing the same molecular basis of apricot material in the Center and the South of Tunisia. These results revealed the efficiency of mapped markers for genetic variability measurements compared to randomly ones, however, no advantage was observed considering the genetic relationships among studied accessions.     

Simple sequence repeat (SSR) analysis for assessment of genetic variability in apricot germplasm

Thirty SSR primer combinations, developed from peach SSR-enriched genomic libraries and BAC libraries of peach [ Prunus persica (L.) Batsch.], were tested for cross amplification with 74 apricot ( Prunus armeniaca L.) germplasm accessions. Twelve primer pairs amplified 14 polymorphic SSR loci useful for discriminating most apricot cultivars, as well as for investigating patterns of variation in apricot germplasm. Levels of polymorphism were higher than the levels described using other codominant marker systems (i.e., isozymes, RFLP markers). Overall, 107 alleles were identified, and all but 11 accessions were unambiguously discriminated. Genetic differentiation of native germplasm into traditional ecogeographical groups was low, with a high level of genetic identity (> 0.75) between the groups. However, neighbor joining cluster analysis of marker distances between cultivars reflected the complex history of apricot domestication, producing groupings not evidently based on the geographical origin of the cultivars. Distant positioning of Chinese cultivars on UPGMA and neighbor joining dendrograms supports the authors' consideration of Chinese apricots as subspecies, Prunus armeniaca var. ansu Maxim., rather than a separate species.     

Genetic structure and differentiation in cultivated grape,Vitis vinifera L

222 cultivated (Vitis vinifera) and 22 wild (V. vinifera ssp. sylvestris) grape accessions were analysed for genetic diversity and differentiation at eight microsatellite loci. A total of 94 alleles were detected, with extensive polymorphism among the accessions. Multivariate relationships among accessions revealed 16 genetic groups structured into three clusters, supporting the classical eco-geographic grouping of grape cultivars: occidentalis, pontica and orientalis. French cultivars appeared to be distinct and showed close affinity to the wild progenitor, ssp. sylvestris from south-western France (Pyrenees) and Tunisia, probably reflecting the origin and domestication history of many of the old wine cultivars from France. There was appreciable level of differentiation between table and wine grape cultivars, and the Muscat types were somewhat distinct within the wine grapes. Contingency chi2 analysis indicated significant heterogeneity in allele frequencies among groups at all loci. The observed heterozygosities for different groups ranged from 0.625 to 0.9 with an overall average of 0.771. Genetic relationships among groups suggested hierarchical differentiation within cultivated grape. The gene diversity analysis indicated narrow divergence among groups and that most variation was found within groups (approximately 85%). Partitioning of diversity suggested that the remaining variation is somewhat structured hierarchically at different levels of differentiation. The overall organization of genetic diversity suggests that the germplasm of cultivated grape represents a single complex gene pool and that its structure is determined by strong artificial selection and a vegetative mode of reproduction.     

Genetic diversity in apricot revealed by AFLP markers: species and cultivar comparisons

The genetic diversity of apricot ( Prunus armeniaca; 2n = 16) was studied using AFLP markers. Forty seven apricot cultivars were selected from the following geographic regions: Europe, North America, North Africa, Turkey, Iran and China. Five EcoRI- MseI AFLP primer combinations revealed 416 legible bands, of which 379 were polymorphic markers. A similarity matrix was prepared using the simple matching coefficient of similarity. A UPGMA dendrogram demonstrated a gradient of decreasing genetic diversity of varieties from the former USSR to Southern Europe. This is coherent with the historical dissemination of apricot from its center of origin in Asia. The American cultivars were intermediate demonstrating a different genetic base than the European and/or Mediterranean cultivars. Euclidean distances from the first ten Factorial Component Analysis coordinate axes were used to generate a tree using the Ward algorithm. The results of these analyses were evaluated based on the known geographic origins and agronomic characteristics of the cultivars studied. Four cultivar groups were identified: Diversification, Geographically Adaptable, Continental Europe and Mediterranean Basin. To evaluate the relationship of the common apricot with some closely related species, one or two accessions of the following related species or sub-species from within the section Armeniaca were included in the analysis: Prunus armeniaca var. ansu, Prunus mume, Prunus brigantiaca, Prunus dasycarpa, and Prunus holosericea. A Neighbour Joining dendrogram was made using the similarity matrix. The P. holosericea accession fell well within the cultivar group, thus supporting its classification as a variant of P. armeniaca. The P. armeniaca var. ansu accession was sister to the common apricot cluster with a bootstrap value of 96%. P. mume was farther removed. P. brigantiaca was the most-distant from the common apricots. P. dasycarpa was intermediate between P. brigantiaca and P. mume, in accord with its plum-apricot hybrid origin. The results have a direct application for the selection of new breeding progenitors.     

Microsatellite variability in apricots (<Emphasis Type="Italic">Prunus armeniaca</Emphasis> L.) reflects their geographic origin and breeding history

A collection of 133 apricot cultivars and three related species originating from different geographical regions were studied with 10 polymorphic microsatellite markers developed in apricot. Altogether, 133 alleles were identified in the set of accessions, with an average of 13.30 alleles per locus. Out of them, 32 alleles occurred only once in the investigated samples, especially in apricots originating from different eco-geographic groups or in different species. The observed heterozygosity for individual loci ranged from 0.8636 to 0.3182, with an average of 0.6281. An unweighted pair group method with arithmetic mean dendrogram based on Nei's genetic distance grouped the accessions according to their eco-geographical origin and/or their pedigree information. Central Asian cultivars have a distinct position on the dendrogram, which supports the assumption that most cultivars have an Asian ancestor. Most East European cultivars analysed cluster together, and the data even revealed a few synonyms. Results show that American cultivars have not only European germ plasm in their pedigree, but they have also been enriched with germ plasm of Asian origin. The implications of these data for the use of simple sequence repeat (SSR) markers as a tool for fingerprinting cultivars in breeders' rights protection and apricot breeding are discussed. In this paper, we demonstrate for the first time the variability of apricot SSRs in a large collection of apricot cultivars and closely related species.     

野生杏和栽培杏的遗传多样性和遗传结构分析

利用SSR分子标记结合荧光毛细管电泳检测技术,研究了野生杏和栽培杏的遗传多样性和遗传结构,结果显示:27个SSR位点,平均每个位点检测到17.82个等位基因(Na)和7.44个有效等位基因(Ne),平均Shannon's信息指数(I)为2.23,平均期望杂合度(He)和观察杂合度(Ho)分别为0.70和0.52。基于SSR位点,群体水平上平均等位基因数、有效等位基因数、期望杂合度、观察杂合度和Shannon's信息指数分别为6.59、4.15、0.70、0.53和1.50,说明我国杏种质资源遗传多样性丰富,其中野生杏资源遗传多样性明显高于栽培杏资源,野生杏中西伯利亚杏种质遗传多样性最高且具有较多的特异等位基因,而栽培杏中仁用杏遗传多样性最低,特有等位基因较少。聚类分析将供试159份种质分为4组。群体遗传结构分析将159份种质划分为5个类群,分类情况与传统形态指标划分基本一致。通过本研究可知,我国杏资源遗传多样性丰富,遗传结构较为复杂;西伯利亚杏与栽培杏亲缘关系较远;野生普通杏与栽培杏具有类似的遗传结构,推测野生普通杏为栽培杏原始种;仁用杏遗传多样性较低,遗传背景狭窄。本研究结果可为杏资源新品种选育及持续利用提供重要的理论依据。     

Database of European chestnut cultivars and definition of a core collection using simple sequence repeats

We have evaluated 271 accessions corresponding to 118 European cultivars, 96 from Spain, 16 from Italy, four from France and two from Portugal with the following objectives: (1) to provide a European database based on reference simple sequence repeats (SSRs) and (2) to define a core collection. A set of 24 highly polymorphic SSRs were used for the genetic analysis. Two main clusters were identified using a model-based Bayesian procedure, which correspond to Spanish and Italian cultivar clusters, with the latter showing a higher genetic diversity. An additional genetic substructure was observed among five different groups of cultivars. A core collection with a minimum of 37 cultivars was selected. We provided a database including 132 European accessions with unique genotypes evaluated with 24 SSRs as a reference for distinction, registering and traceability. Finally, we found that a core collection based on 14% of the total accessions conserves all allelic diversity.     

Identification and analysis of genetic variation among rose cultivars using random amplified polymorphic DNA

Identified germplasm is an important component for efficient and effective management of plant genetic resources. Traditionally, cultivars or species identification has relied on morphological characters like growth habit or floral morphology like flower colour and other characteristics of the plant. Studies were undertaken for identification and analysis of genetic variation within 34 rose cultivars through random amplified polymorphic DNA (RAPD) markers. Analysis was made by using twenty five decamer primers. Out of twenty five, ten primers were selected and used for identification and analysis of genetic relationships among 34 rose cultivars. A total of 162 distinct DNA fragments ranging from 0.1 to 3.4 kb was amplified by using 10 selected random decamer primers. The genetic similarity was evaluated on the basis of presence or absence of bands. The cluster analysis indicated that the 34 rose cultivars form 9 clusters. The first cluster consists of eight hybrid cultivars, three clusters having five cultivars each, one cluster having four cultivars, two clusters having three cultivars each and two clusters having one cultivar each. The genetic distance was very close within the cultivars. Thus, these RAPD markers have the potential for identification of clusters and characterization of genetic variation within the cultivars. This is also helpful in rose breeding programs and provides a major input into conservation biology.     

Genetic structure and differentiation in cultivated fig (<Emphasis Type="Italic">Ficus carica</Emphasis> L.)

One hundred ninety-four germplasm accessions of fig representing the four fig types, Common, Smyrna, San Pedro, and Caprifig were analyzed for genetic diversity, structure, and differentiation using genetic polymorphism at 15 microsatellite loci. The collection showed considerable polymorphism with observed number of alleles per locus ranging from four for five different loci, MFC4, LMFC14, LMFC22, LMFC31 and LMFC35 to nine for LMFC30 with an average of 4.9 alleles per locus. Seven of the 15 loci included in the genetic structure analyses exhibited significant deviation from panmixia, of which two showed excess and five showed deficiency of heterozygote. The cluster analysis (CA) revealed ten groups with 32 instances of synonymy among cultivars and groups differed significantly for frequency and composition of alleles for different loci. The principal components analysis (PCA) confirmed the results of CA with some groups more differentiated than the others. Further, the model based Bayesian approach clustering suggested a subtle population structure with mixed ancestry for most figs. The gene diversity analysis indicated that much of the total variation is found within groups (H _G /H _T = 0.853; 85.3%) and the among groups within total component (G _GT = 0.147) accounted for the remaining 14.7%, of which ~64% accounted for among groups within clusters (G _GC = 0.094) and ~36% among clusters (G _CT = 0.053). The analysis of molecular variance (AMOVA) showed approximately similar results with nearly 87% of variation within groups and ~10% among groups within clusters, and ~3% among clusters. Overall, the gene pool of cultivated fig analyzed possesses substantial genetic polymorphism but exhibits narrow differentiation. It is evident that fig accessions from Turkmenistan are somewhat genetically different from the rest of the Mediterranean and the Caucasus figs. The long history of domestication and cultivation with widespread dispersal of cultivars with many synonyms has resulted in a great deal of confusion in the identification and classification of cultivars in fig.     

Localisation and movement of Plum pox virus in apricot stem tissues

Localisation and movement of Plum pox virus (PPV), sharka disease, in stem tissues of susceptible and resistant apricot (Prunus armeniaca L.) cultivars was studied. Two different assays were performed. In the first assay, apricot cultivars were grafted on to a non‐inoculated GF305 peach rootstock and, after two months, the sprouted apricot was inoculated by chip‐grafting. In the second assay, apricot cultivars were grafted on to a previously chip‐inoculated GF305 showing strong PPV symptoms. Localisation of virus was studied in apricot stem by immuno‐tissue printing and sharka symptoms in GF305 and apricot leaves were also observed. Virus was mainly localised in the xylem, and sometimes in the cortex and pith. Results revealed that, while all the cultivars allowed limited virus movement from the inoculation point, only the susceptible cultivars (Screara, Bebeco and Colomer) allowed long distance movement and even showed symptoms in leaves.     

Genetic diversity and relationships within sweet kernel apricot and related Armeniaca species based on sequence-related amplified polymorphism markers

Sequence-related amplified polymorphism (SRAP) markers were employed to detect the genetic variation among 28 sweet kernel apricot and related Armeniaca accessions from China. Fifteen SRAP primer combinations were used and 252 polymorphic bands out of 286 with an average of 16.8 per primer combination were observed. The unweighted pair-group method (UPGMA) analysis demonstrated that the accessions had a similarity range from 0.55 to 0.91 with a mean of 0.7, and there were three clusters with two groups of sweet kernel apricots distinctly separated from the related Armeniaca vulgaris and Armeniaca sibirica at the similarity level of 0.58, indicating more extensive genetic variation among sweet kernel apricot. The origin of sweet kernel apricot has also been discussed. This suggested there are abundant germplasm resources of sweet kernel apricot from China for further breeding and biodiversity conservation.     

Microsatellite markers reveal multiple origins for Italian weedy rice

Weedy rice (Oryza sativa L.) is one of the major issues of rice cultivation worldwide. In Italy, it infests about 70% of the total rice area. Different Weedy Rice populations can be distinguished based on variable morphological and physiological traits; however, little is known about genetic differentiation and origin of Italian weedy rice populations. The objective of this study was to genetically and morphologically characterize and compare different Italian weedy rice populations selected on the basis of different phenotypes. The main Italian rice territory was divided into 10 geographical areas in which 40 weedy rice populations were collected and grouped according to the awn traits. All the individuals of the populations were morphologically characterized according to plant and seed traits. Genetic characterization was performed using 19 SSR markers on all the collected accessions, and several rice cultivars, including some very old (late 19th century), nowadays are no longer cultivated. ANOVA showed that morphological plant and seed traits were significantly affected by the collection area and awnedness group. The importance of the awn morphology was also reflected in the Bayesian clustering where, despite a relatively low genetic diversity, the clusters displayed different awn types. An UPGMA dendrogram confirmed the clusters detected in STRUCTURE analysis and also revealed a grouping of certain old cultivars with the weedy rice, suggesting a common origin.     

Loss of genetic diversity as a signature of apricot domestication and diffusion into the Mediterranean Basin

ABSTRACT: BACKGROUND: Domestication generally implies a loss of diversity in crop species relative to their wild ancestors because of genetic drift through bottleneck effects. Compared to native Mediterranean fruit species like olive and grape, the loss of genetic diversity is expected to be more substantial for fruit species introduced into Mediterranean areas such as apricot (Prunus armeniaca L.), which was probably primarily domesticated in China. By comparing genetic diversity among regional apricot gene pools in several Mediterranean areas, we investigated the loss of genetic diversity associated with apricot selection and diffusion into the Mediterranean Basin. RESULTS: According to the geographic origin of apricots and using Bayesian clustering of genotypes, Mediterranean apricot (207 genotypes) was structured into three main gene pools: 'Irano-Caucasian', 'North Mediterranean Basin' and 'South Mediterranean Basin'. Among the 25 microsatellite markers used, only one displayed deviations from the frequencies expected under neutrality. Similar genetic diversity parameters were obtained within each of the three main clusters using both all SSR loci and only 24 SSR loci based on the assumption of neutrality. A significant loss of genetic diversity, as assessed by the allelic richness and private allelic richness, was revealed from the 'Irano-Caucasian' gene pool, considered as a secondary centre of diversification, to the northern and southwestern Mediterranean Basin. A substantial proportion of shared alleles was specifically detected when comparing gene pools from the 'North Mediterranean Basin' and 'South Mediterranean Basin' to the secondary centre of diversification. CONCLUSIONS: A marked domestication bottleneck was detected with microsatellite markers in the Mediterranean apricot material, depicting a global image of two diffusion routes from the 'Irano-Caucasian' gene pool: North Mediterranean and Southwest Mediterranean. This study generated genetic insight that will be useful for management of Mediterranean apricot germplasm as well as genetic selection programs related to adaptive traits.     

Genetic relationship among cultivated and wild grapevine accessions from Tunisia.

We have used nuclear and chloroplast molecular markers to genotype cultivated and wild accessions of Vitis vinifera L. from Tunisia and assess their genetic relationships. Fifty-five distinct genotypes were identified among 80 cultivated accessions, including 18 genotypic groups containing between 2 and 5 accessions per group. They could represent a total of 60 distinct cultivars owing to berry colour variation found within identical genotype groups. Most of the 55 genotypes represent unique table grape genotypes except for one of them that was found identical to the genotype of table grape cultivar Rosseti. Hybridization among cultivars as well as self pollinations seems to have played an important role in their origin since several groups of closely related cultivars were observed. Furthermore, a parentage analysis showed a high probability for a parent hybrid relationship within two groups of three cultivars. No strong genetic similarities were found between cultivated and wild samples indicating that the cultivated accessions do not derive from local Vitis vinifera L. populations but could have been introduced from other regions in historic times.     

Microsatellite variability in grapevine cultivars from different European regions and evaluation of assignment testing to assess the geographic origin of cultivars

Nine microsatellite markers (VVMD5, VVMD7, VVS2, ssrVrZAG21, ssrVrZAG47, ssrVrZAG62, ssrVrZAG64, ssrVrZAG79 and ssrVrZAG83) were chosen for the analysis of marker information content, the genetic structure of grapevine cultivar gene pools, and differentiation among grapevines sampled from seven European vine-growing regions (Greece, Croatia, North Italy, Austria and Germany, France, Spain and Portugal). The markers were found to be highly informative in all cultivar groups and therefore constitute a useful set for the genetic characterization of European grapevines. Similar and high levels of genetic variability were detected in all investigated grapevine gene pools. Genetic differentiation among cultivars from different regions was significant, even in the case of adjacent groups such as the Spanish and Portuguese cultivars. No genetic differentiation could be detected between vines with blue and white grapes, indicating that they have undergone the processes of cultivar development jointly. The observed genetic differentiation among vine-growing regions suggested that cultivars could possibly be assigned to their regions of origin according to their genotypes. This might allow one to determine the geographical origin of cultivars with an unknown background. The assignment procedure proved to work for cultivars from the higher differentiated regions, as for example from Austria and Portugal. Received: 10 April 1999 / Accepted: 25 May 1999     

Centennial olive trees as a reservoir of genetic diversity

Background and Aims

Genetic characterization and phylogenetic analysis of the oldest trees could be a powerful tool both for germplasm collection and for understanding the earliest origins of clonally propagated fruit crops. The olive tree (Olea europaea L.) is a suitable model to study the origin of cultivars due to its long lifespan, resulting in the existence of both centennial and millennial trees across the Mediterranean Basin.

Methods

The genetic identity and diversity as well as the phylogenetic relationships among the oldest wild and cultivated olives of southern Spain were evaluated by analysing simple sequence repeat markers. Samples from both the canopy and the roots of each tree were analysed to distinguish which trees were self-rooted and which were grafted. The ancient olives were also put into chronological order to infer the antiquity of traditional olive cultivars.

Key Results

Only 9·6 % out of 104 a priori cultivated ancient genotypes matched current olive cultivars. The percentage of unidentified genotypes was higher among the oldest olives, which could be because they belong to ancient unknown cultivars or because of possible intra-cultivar variability. Comparing the observed patterns of genetic variation made it possible to distinguish which trees were grafted onto putative wild olives.

Conclusions

This study of ancient olives has been fruitful both for germplasm collection and for enlarging our knowledge about olive domestication. The findings suggest that grafting pre-existing wild olives with olive cultivars was linked to the beginnings of olive growing. Additionally, the low number of genotypes identified in current cultivars points out that the ancient olives from southern Spain constitute a priceless reservoir of genetic diversity.     

Simple Sequence Repeat Analysis of Genetic Diversity in Primary Core Collection of Peach （Prunus persica）

In this study, the genetic diversity of 51 cultivars in the primary core collection of peach （Prunus persica （L.） Batsch） was evaluated by using simple sequence repeats （SSRs）. The phylogenetic relationships and the evolutionary history among different cultivars were determined on the basis of SSR data. Twenty-two polymorphic SSR primer pairs were selected, and a total of 111 alleles were identified in the 51 cultivars, with an average of 5 alleles per locus. According to traditional Chinese classification of peach cultivars, the 51 cultivars in the peach primary core collection belong to six variety groups. The SSR analysis revealed that the levels of the genetic diversity within each variety group were ranked as Sweet peach 〉 Crisp peach 〉 Flat peach 〉 Nectarine 〉 Honey Peach 〉 Yellow fleshed peach. The genetic diversity among the Chinese cultivars was higher than that among the introduced cultivars. Cluster analysis by the unweighted pair group method with arithmetic averaging （UPGMA） placed the 51 cultivars into five linkage clusters. Cultivar members from the same variety group were distributed in different UPGMA clusters and some members from different variety groups were placed under the same cluster. Different variety groups could not be differentiated in accordance with SSR markers. The SSR analysis revealed rich genetic diversity in the peach primary core collection, representative of genetic resources of peach.     

Differentiation and phylogenetic relationship among different cultivars of asparagus bean (Vigna unguiculata ssp. sesquipedalis) assessed using ISSR markers

Asparagus bean, one of the three subspecies of Vigna unguiculata, has a long cultivation history in China. The genetic diversity was analyzed based on the 66 landraces and cultivars cultivated in China by using ISSR molecular markers, with which 192 amplification loci were obtained 32.3% of them being polymorphic. The genetic differentiation analysis revealed a very high genetic diversity in the Chinese landraces, which confirmed that China is the secondary origin centre of the asparagus bean. The commercial cultivars bred in China were genetically highly homogenous, suggesting that the breeding process has resulted in disappearance of some of the genetic variation. A cluster analysis at 0.17 of Nei genetic distance divided the 66 landraces and cultivars into 9 groups. Their clustering pattern basically matches the phylogeny of those cultivars, and also corresponds to their geographical origin and morphological traits.     

Genetic diversity and association mapping in a collection of selected Chinese soybean accessions based on SSR marker analysis

For broadening the narrow genetic base of modern soybean cultivars, 159 accessions were selected from the Chinese soybean collection which contained at least one of seven important agronomic traits: resistance to soybean cyst nematode (SCN) or soybean mosaic virus (SMV), tolerance to salt, cold, or drought, high seed oil content or high protein content. Genetic diversity evaluation using 55 microsatellite loci distributed across the genome indicated that a large amount of genetic diversity (0.806) and allelic variation (781) were conserved in this selected set, which captured 65.6% of the alleles present in Chinese soybean collection (1,863 accessions). On average, 9.4 rare alleles (frequency <5%) per locus were present, which were highly informative. Using model-based Bayesian clustering in STRUCTURE we distinguished four main clusters and a set of accessions with admixed ancestry. The four clusters reflected different geographic regions of origin of the accessions. Since the clusters were also clearly different with respect to the seven agronomic traits, the inferred population structure was introduced when association analysis was conducted. A total of 21 SSR markers on 16 chromosomes were identified as significantly (P < 0.01) associated with high oil content (6), high protein content (1), drought tolerance (5), SCN resistance (6) and SMV resistance (3). Twelve of these markers were located in or near previously identified quantitative trait loci (QTL). The results for both genetic relationship and trait-related markers will be useful for effective conservation and utilization of soybean germplasm.     

蒙古冰草遗传多样性的RAPD分析

采用RAPD技术对蒙古冰草（Agropyron mongolicum Keng)6个天然居群和2个栽培品种（系）的45个个体进行了遗传多样性检测。17个引物共检测到101个位点,其中多态位点81个,占80.2%,相对于其它小麦族植物,显示出了较高的遗传多样性,多样性指数（DC）分析的结果表明,遗传多样性在居群内和居群间的分布存在不均衡现象,但总体来看,居群内的遗传变异高于居群间,这是由蒙古冰草异花,风媒传粉的外繁育系统所决定的,在天然居群与栽培品种（系）间,前者的DC值为0.250,后者的DC值为0.181,而且前者的平均遗传距离（0.290)也高于后者（0.213),表明天然居群间的遗传分化大于栽培品种（系）,这与天然居群间环境的异质性密切相关,同时也反映了栽培品种（系）间较近的亲缘关系,UPG-MA聚类分析的结果表明,8个居群基本上可被分为与其生境特点及生长条件相适应的3个类群,反映了自然选择及人工选择对居群间遗传分化的巨大影响。