RAPD analysis of the genetic diversity of mango (Mangifera indica) germplasm in Brazil

We evaluated genetic variability of mango (Mangifera indica) accessions maintained in the Active Germplasm Bank of Embrapa Meio-Norte in Teresina, Piauí, Brazil, using RAPDs. Among these accessions, 35 originated from plantings in Brazil, six from the USA and one from India. Genomic DNA, extracted from leaf material using a commercial purification kit, was subjected to PCR with the primers A01, A09, G03, G10, N05, and M16. Fifty-five polymorphic loci were identified, with mean of 9.16 ± 3.31 bands per primer and 100% polymorphism. Application of unweighted pair group method using arithmetic average cluster analysis demonstrated five genotypic groups among the accessions examined. The genotypes Rosa 41, Rosa 48 and Rosa 49 were highly similar (94% similarity), whereas genotypes Sensation and Rosa 18 were the most divergent (only 7% similarity). The mango accessions were found to have considerable genetic variability, demonstrating the importance of analyzing each genotype in a collection in order to efficiently maintain the germplasm collection.     

Evaluation of AFLPs for germplasm fingerprinting and assessment of genetic diversity in cultivars of tomato (Lycopersicon esculentum L.).

Cultivated tomato (L. esculentum L.) germplasm exhibits limited genetic variation compared with wild Lycopersicon species. Amplified fragment length polymorphism (AFLP) markers were used to evaluate genetic variation among 74 cultivars, primarily from California, and to fingerprint germplasm to determine if cultivar-specific patterns could be obtained. All 74 cultivars were genotyped using 26 AFLP primer combinations; of the 1092 bands scored, 102 AFLP bands (9.3%) were polymorphic. Pair-wise genetic similarity coefficients (Jaccard and Nei-Li) were calculated. Jaccard coefficients varied from 0.16 to 0.98 among cultivar pairs, and 72% of pair-wise comparisons exceeded 0.5. UPGMA (unweighted pair-group method with arithmetic averaging) clustering and principle component analysis revealed four main clusters, I-IV; most modern hybrid cultivars grouped in II, whereas most vintage cultivars grouped in I. Clusters III and IV contained three and two cultivars, respectively. Some groups of cultivars closely related by pedigree exhibited high bootstrap values, but lower values (<50%) were obtained for cluster II and its four subgroups. Unique fingerprints for all 74 cultivars were obtained by a minimum of seven AFLP primer pairs, despite inclusion of some closely related cultivars. This study demonstrated that AFLP markers are effective for obtaining unique fingerprints of, and assessing genetic diversity among, tomato cultivars.     

Restriction fragment variation in the nuclear and chloroplast genomes of cultivated and wild Sorghum bicolor

Summary Fifty-six accessions of cultivated and wild sorghum were surveyed for genetic diversity using 50 low-copy-number nuclear DNA sequence probes to detect restriction fragment length polymorphisms (RFLPs). These probes revealed greater genetic diversity in wild sorghum than in cultivated sorghum, including a larger number of alleles per locus and a greater portion of polymorphic loci in wild sorghum. In comparison to previously published isozyme analyses of the same accessions, RFLP analysis reveals a greater number of alleles per locus. Furthermore, many RFLP alleles have frequencies between 0.25–0.75, while the vast majority of isozyme alleles are either rare (< 0.25) or near fixation (> 0.75). Correlations between genetic and geographic distances among the accessions were stronger when calculated with RFLP than with isozyme data. Systematic relationships revealed by nuclear and chloroplast restriction site analysis indicate that cultivated sorghum is derived from the wild ssp. arundinaceum. The portion of the wild gene pool most genetically similar to the cultivars is from central-northeastern Africa. Previous published data also suggested that this is most likely the principal area of domestication of sorghum. Introgression between wild and cultivated sorghum was inferred from disconcordant relationships shown by nuclear and chloroplast DNA markers. Introgression apparently occurs infrequently enough that the crop and its wild relatives maintain distinct genetic constitutions.     

Genetic diversity and relationships among Dutch elm disease tolerant Ulmus pumila L. accessions from China.

Elm breeding programs worldwide have relied heavily on Asian elm germplasm, particularly Ulmus pumila, for the breeding of Dutch elm disease tolerant cultivars. However, the extent and patterning of genetic variation in Asian elm species is unknown. Therefore, the objective of this research was to determine the extent of genetic diversity among 53 U. pumila accessions collected throughout the People's Republic of China. Using 23 microsatellite loci recently developed in the genus Ulmus, a total of 94 alleles were identified in 15 polymorphic and 4 monomorphic loci. The average number of alleles per locus was 4.9, with a range of 1-11 alleles. Gene diversity estimates per locus ranged from 0.08 to 0.87, and the non-exclusion probability for the 15 polymorphic loci combined was 0.7 x 10(-9). Nineteen region-specific alleles were identified, and regional gene diversity estimates were moderately high (0.48-0.57). The genetic relationships among accessions and regions were estimated by UPGMA and principal coordinate analysis. Both techniques discriminated all accessions and regions. Two microsatellite markers (UR175 + UR123 or Ulm-3) were sufficient to discriminate up to 99.7% of the accessions studied. This research provides useful information for DNA-based fingerprinting, breeding, ecological studies, and diversity assessment of elm germplasm.     

The comparison of RFLP,RAPD, AFLP and SSR (microsatellite) markers for germplasm analysis

The utility of RFLP (restriction fragment length polymorphism), RAPD (random-amplified polymorphic DNA), AFLP (amplified fragment length polymorphism) and SSR (simple sequence repeat, microsatellite) markers in soybean germplasm analysis was determined by evaluating information content (expected heterozygosity), number of loci simultaneously analyzed per experiment (multiplex ratio) and effectiveness in assessing relationships between accessions. SSR markers have the highest expected heterozygosity (0.60), while AFLP markers have the highest effective multiplex ratio (19). A single parameter, defined as the marker index, which is the product of expected heterozygosity and multiplex ratio, may be used to evaluate overall utility of a marker system. A comparison of genetic similarity matrices revealed that, if the comparison involved both cultivated (Glycine max) and wild soybean (Glycine soja) accessions, estimates based on RFLPs, AFLPs and SSRs are highly correlated, indicating congruence between these assays. However, correlations of RAPD marker data with those obtained using other marker systems were lower. This is because RAPDs produce higher estimates of interspecific similarities. If the comparisons involvedG. max only, then overall correlations between marker systems are significantly lower. WithinG. max, RAPD and AFLP similarity estimates are more closely correlated than those involving other marker systems.Abbreviations RFLP restriction fragment length plymorphism - RAPD random-amplified polymorphic DNA - AFLP amplified fragment length polymorphism - SSR simple sequence repeat - PCR polymerase chain reaction - TBE Tris-borate-EDTA buffer - MI marker index - SENA sum of effective numbers of alleles     

Genetic relationships among domesticated and wild sunflowers (Helianthus annuus,Asteraceae)

Randomly amplified polymorphic DNA (RAPD) loci were used to investigate the origin and genetic relationships of the domesticated sunflower and its wild relatives. A total of 13 primers was employed for the PCR amplifications, from which 68 polymorphic loci were scored. Analysis of RAPD data supports the origin of the domesticated sunflower from wildH. annuus. The high RAPD identity between wild and domesticatedH. annuus (I = 0.976 to I = 0.997) is concordant with a progenitorderivative relationship. However, the identities are very high and therefore provide little information regarding the geographic origin of the domesticated sunflower. Nonetheless, some inferences concerning relationships among domesticated sunflower accessions can be made. The native American varieties and old landracesform a genetically cohesive group based on RAPD evidence, probably due to their origin prior to the use of interspecific hybridization in the development of sunflower cultivars. In contrast, the modern cultivars are not genetically cohesive, perhaps due to the extensive use of intraspecific and interspecific hybridization in the development of modern sunflower varieties. Likewise, little concordance was observed between the geographical origin and genetic clustering of wild populations—an observation probably best explained by the weedy, human dispersed nature of wildH. annuus populations. The information presented here may be a reliable indicator of genetic relationships among wild and domesticated sunflower accessions. However, the processes generating the observed relationships are complex, and the occurrence of unexpected groupings or absence of predicted ones will probably remain difficult to understand.     

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.     

Direct comparison of levels of genetic variation in tomato detected by a GACA-containing microsatellite probe and by random amplified polymorphic DNA.

In this study, a direct comparison was made of the ability of four selected random amplified polymorphic DNA (RAPD) primers and a GACA-containing microsatellite probe to detect genetic variation in Lycopersicon. Of the 89 RAPD primers initially tested, 85 showed differences between a representative of Lycopersicon pennellii and L. esculentum, but only 4 distinguished among three L. esculentum cultivars. These four primers were subsequently tested on representatives of six Lycopersicon species. In pairwise comparisons of species, all or 14 of the 15 combinations could be distinguished by single primers. When the primers were tested on 15 L. esculentum cultivars, 90 of the 105 combinations could be distinguished by the four primers together. Finally, none of 118 tested primers showed reproducible differences among calli or progeny of régénérants from tissue culture, although some of the plants had inherited morphological mutations. The probe pWVA16, which detects GACA-containing microsatellites, could distinguish in TaqI-digested DNA the representatives of Lycopersicon species as well as all the L. esculentum cultivars tested. The probe was unable to detect polymorphisms among calli and the progeny of regenerants from tissue culture. An analysis of the results showed that the four selected RAPD primers were able to detect polymorphic bands among species at a frequency of 80%, and among cultivars at a frequency of 44%. In contrast, the microsatellite probe detected polymorphic bands at a frequency of 100 and 95%, respectively. The GACA-containing probe did not detect any common bands among the representatives of the six species, while band sharing with RAPDs was 48%. These results indicate that the two methods detect two types of DNA that differ in their degree of variability.     

Efficiency of RFLP, RAPD, and AFLP markers for the construction of an intraspecific map of the tomato genome.

We have constructed a tomato genetic linkage map based on an intraspecific cross between two inbred lines of Lycopersicon esculentum and L. esculentum var. cerasiforme. The segregating population was composed of 153 recombinant inbred lines. This map is comprised of one morphological, 132 RFLP (restriction fragment length polymorphism, including 16 known-function genes), 33 RAPD (random amplified polymorphic DNA), and 211 AFLP (amplified fragment length polymorphism) loci. We compared the 3 types of markers for their polymorphism, segregation, and distribution over the genome. RFLP, RAPD, and AFLP methods revealed 8.7%, 15.8%, and 14.5% informative bands, respectively. This corresponded to polymorphism in 30% of RFLP probes, 32% of RAPD primers, and 100% of AFLP primer combinations. Less deviation from the 1:1 expected ratio was obtained with RFLP than with AFLP loci (8% and 18%, respectively). RAPD and AFLP markers were not randomly distributed over the genome. Most of them (60% and 80%, respectively) were grouped in clusters located around putative centromeric regions. This intraspecific map spans 965 cM with an average distance of 8.3 cM between markers (of the framework map). It was compared to other published interspecific maps of tomato. Despite the intraspecific origin of this map, it did not show any increase in length when compared to the high-density interspecific map of tomato.     

用RFLP标记分析甘蓝型油菜的遗传多样性

以甘蓝型油菜的２８个基因组探针和两种限制性内切酶对包括４６个中国品种、９个欧洲品种在内的５９个甘蓝型油菜品种（系）的ＲＦＬＰ标记进行了分析。在放射自显影胶片上,共检测到４１０条具多态性的分子杂交带,表明甘蓝型油菜中存在着极为丰富的遗传变异。聚类分析结果表明,在相似性为４５％的水平上,可把中国甘蓝型油菜划分为６组：胜利油菜组、跃进油菜组、中油８２１组、远缘种质组、优质油菜组和变异不详组。欧洲冬油菜与以上６组存在着较显著的遗传距离。主成分分析的结果与上述分组较为一致。以上结果表明,对于扩大中国甘蓝型油菜的遗传基础,欧洲冬油菜无疑是一个重要的种质资源。另一方面,用典型的中国甘蓝型油菜与欧洲冬油菜配制的杂交种,较易产生强大的杂种优势。从对已进行了染色体定位的６１条放射自显影带的分析看,无论是上述分组内,还是分组间,ＲＦＬＰ的相对差异均主要表现在Ａ基因组中。讨论了致使Ａ基因组遗传变异较大的可能因素。     

80份甘蔗种质RAMP标记遗传多样性分析

采用RAMP分子标记技术对80份甘蔗种质(32份祖亲种、48份栽培品种或品系)的遗传基础进行了分析。从30对引物组合中筛选出4对多态性较强引物,构建了甘蔗80份种质的RAMP指纹图谱,这四对引物组合共扩增出84条带,其多态性为91.7%。80份种质的遗传相似系数变化范围在0.433～0.988,平均0.710。聚类分析表明,随着相似系数结合线的不同,可分别将参试的甘蔗种质从属间(甘蔗属与斑茅种)、野生种(割手密种、大茎野生种、印度种、中国种)与栽培种(热带种)间、栽培种与杂交栽培品种(或品系)间区别开来。各祖亲种与杂交栽培品种(或品系)的遗传相似性由大到小依次为热带种>印度种和中国种>大茎野生种＞云南割手密种＞其它割手密种＞斑茅。另外,本试验首次利用RAMP标记,获得了部分热带种、野生种及斑茅种特异片段,并发现这些特异片段能不同程度地在具有其血缘的栽培种中得到传递。     

Comparison of RAPD and RFLP genetic markers in determining genetic similarity among Brassica oleracea L. genotypes

Genetic similarity among 45 Brassica Oleracea genotypes was compared using two molecular markers, random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphisms (RFLPs). The genotypes included 37 broccolis (var. italica), five cauliflowers (var. botrytis) and three cabbages (var. capitata) which represented a wide range of commercially-available germplasm, and included open-pollinated cultivars, commercial hybrids, and inbred parents of hybrid cultivars. Fifty-six polymorphic RFLP bands and 181 polymorphic RAPD bands were generated using 15 random cDNA probes and 62 10-mer primers, respectively. The objectives were to compare RFLP and RAPD markers with regard to their (1) sampling variance, (2) rank correlations of genetic distance among sub-samples, and (3) inheritance. A bootstrap procedure was used to generate 200 random samples of size n (n=2,3,5,... 55) independently from the RAPD and RFLP data sets. The coefficient of variance (CV) was estimated for each sample. Pooled regressions of the coefficient of variance on bootstrap sample size indicated that the rate of decrease in CV with increasing sample size was the same for RFLPs and RAPDs. The rank correlation between the Nei-Li genetic similarity values for all pairs of genotypes (990) based on RFLP and RAPD data was 0.745. Differences were observed between the RFLP and RAPD dendrograms of the 45 genotypes. Overlap in the distributions of rank correlations between independent sub-samples from the RAPD data set, compared to correlations between RFLP and RAPD sub-samples, suggest that observed differences in estimation of genetic similarity between RAPDs and RFLPs is largely due to sampling error rather than due to DNA-based differences in how RAPDs and RFLPs reveal polymorphisms. A crossing algorithm was used to generate hypothetical banding patterns of hybrids based on the genotypes of the parents. The results of this study indicate that RAPDs provide a level of resolution equivalent to RFLPs for detemination of the genetic relationships among genotypes.     

Assessment of genetic variation and differentiation of hop genotypes by microsatellite and AFLP markers.

Microsatellites have many desirable marker properties and have been increasingly used in crop plants in genetic diversity studies. Here we report on the characterisation of microsatellite markers and on their use for the determination of genetic identities and the assessment of genetic variability among accessions from a germplasm collection of hop. Thirty-two polymorphic alleles were found in the 55 diploid genotypes, with an average number of eight alleles (3.4 effective alleles) for four microsatellite loci. Calculated polymorphic information content values classified three loci as informative markers and two loci as suitable for mapping. The average observed heterozygosity was 0.7 and the common probability of identical genotypes was 3.271 x 10(-4). An additional locus, amplified by one primer pair, was confirmed by segregation analysis of two crosses. The locus discovered was heterozygous, with a null allele in the segregating population. The same range of alleles was detected in nine triploid and five tetraploid hop genotypes. Cultivar heterozygosity varied among all 69 accessions, with only one cultivar being homozygous at four loci. Microsatellite allele polymorphisms distinguished 81% of all genotypes; the same allelic profile was found mainly in clonally selected cultivars. Cultivar-specific alleles were found in some genotypes, as well as a specific distribution of alleles in geographically distinct hop germplasms. The genetic relationship among 41 hop accessions was compared on the basis of microsatellite and AFLP polymorphisms. Genetic similarity dendrograms showed low correlation between the two marker systems. The microsatellite dendrogram grouped genetically related accessions reasonably well, while the AFLP dendrogram showed good clustering of closely related accessions and, additionally, separated two geographically distinct hop germplasms. The results of microsatellite and AFLP analysis are discussed from the point of view of the applicability of the two marker systems for different aspects of germplasm evaluation.     

Direct comparison of levels of genetic variation among barley accessions detected by RFLPs, AFLPs, SSRs and RAPDs

 RFLPs, AFLPs, RAPDs and SSRs were used to determine the genetic relationships among 18 cultivated barley accessions and the results compared to pedigree relationships where these were available. All of the approaches were able to uniquely fingerprint each of the accessions. The four assays differed in the amount of polymorphism detected. For example, all 13 SSR primers were polymorphic, with an average of 5.7 alleles per primer set, while nearly 54% of the fragments generated using AFLPs were monomorphic. The highest diversity index was observed for AFLPs (0.937) and the lowest for RFLP (0.322). Principal co-ordinate analysis (PCoA) clearly separated the spring types from the winter types using RFLP and AFLP data with the two-row winter types forming an intermediate group. Only a small group of spring types clustered together using SSR data with the two-row and six-row winter varieties more widely dispersed. Direct comparisons between genetic similarity (GS) estimates revealed by each of the assays were measured by a number of approaches. Spearman rank correlation ranked over 70% of the pairwise comparisons between AFLPs and RFLPs in the same order. SSRs had the lowest values when compared to the other three assays. These results are discussed in terms of the choice of appropriate technology for different aspects of germplasm evaluation.     

基于SRAP和TRAP标记的河北野生狗牙根种质遗传多样性分析

以SRAP和TRAP 2种标记技术对36份狗牙根材料的遗传多样性及亲缘关系进行了分析,其中包含34份河北省野生狗牙根种质资源。分别由238对SRAP和85对TRAP引物组合中筛选获得具有多态性的SRAP和TRAP引物组合各10对,PCR扩增总条带分别为186和161条,多态性条带156和132条,平均每对引物扩增出多态性条带各15.6和13.2条,多态性位点比率分别为83.4%和81.0%。2种标记合并进行聚类分析,所有供试的36份狗牙根材料遗传相似系数GS=0.519~0.983,平均为0.7。当GS=0.68时,可将36份供试材料分为4个类群。本研究结果表明河北野生狗牙根种质资源存在较丰富的遗传多样性,可为种质资源保护和选育优良狗牙根新品种提供科学依据。     

Genetic diversity of cultivated flax (Linum usitatissimum L.) germplasm assessed by retrotransposon-based markers

Retrotransposon segments were characterized and inter-retrotransposon amplified polymorphism (IRAP) markers developed for cultivated flax (Linum usitatissimum L.) and the Linum genus. Over 75 distinct long terminal repeat retrotransposon segments were cloned, the first set for Linum, and specific primers designed for them. IRAP was then used to evaluate genetic diversity among 708 accessions of cultivated flax comprising 143 landraces, 387 varieties, and 178 breeding lines. These included both traditional and modern, oil (86), fiber (351), and combined-use (271) accessions, originating from 36 countries, and 10 wild Linum species. The set of 10 most polymorphic primers yielded 141 reproducible informative data points per accession, with 52% polymorphism and a 0.34 Shannon diversity index. The maximal genetic diversity was detected among wild Linum species (100% IRAP polymorphism and 0.57 Jaccard similarity), while diversity within cultivated germplasm decreased from landraces (58%, 0.63) to breeding lines (48%, 0.85) and cultivars (50%, 0.81). Application of Bayesian methods for clustering resulted in the robust identification of 20 clusters of accessions, which were unstratified according to origin or user type. This indicates an overlap in genetic diversity despite disruptive selection for fiber versus oil types. Nevertheless, eight clusters contained high proportions (70?C100%) of commercial cultivars, whereas two clusters were rich (60%) in landraces. These findings provide a basis for better flax germplasm management, core collection establishment, and exploration of diversity in breeding, as well as for exploration of the role of retrotransposons in flax genome dynamics.     

Species relationships in Fagopyrum revealed by PCR-based DNA fingerprinting

Random amplified polymorphic DNA (RAPD) markers were used to distinguish between 28 different accessions belonging to 14 species and two sub-species of Fagopyrum. Of the 75 random 10-mer primers tested, only 19 generated robust, easily interpretable amplification products. A total of 364 bands were observed with an average of 19.15 bands per primer, of which 99.45% were polymorphic. Primer OPN-08 produced the maximum number of fragments and UBC-183 produced the minimum number of fragments. The data were utilized to elucidate genetic relationships among 14 species and two sub-species of Fagopyrum. Cluster analysis using the unweighted paired group method of arithmetic means (UPGMA) showed four main clusters, two each of the cymosum and urophyllum groups. The results showed that Fagopyrum tataricum is closer to its wild ancestor F. tataricum ssp. potanini Batalin, closely followed by Fagopyrum giganteum. Cultivated common buckwheat ( Fagopyrum esculentum) showed affinity with its putative wild ancestor F. esculentum ssp. ancestrale and the other closely related diploid species Fagopyrum homotropicum. In the urophyllum group, Fagopyrum macrocarpum and Fagopyrum pleioramosum formed one cluster, whereas Fagopyrum capillatum, Fagopyrum gracilipes and Fagopyrum gilessii clustered separately. Except for a few cases, our results correspond with previously reported studies on Fagopyrum using the isozyme, RFLP and RAPD methods. Species-diagnostic amplification products specific to some species in the cymosum and urophyllum groups were identified. Our results show that RAPDs can be successfully used to analyze species relationships in Fagopyrum and also for constructing linkage maps.     

Genetic diversity of wild grapevine populations in Spain and their genetic relationships with cultivated grapevines

The wild grapevine, Vitis vinifera L. ssp. sylvestris (Gmelin) Hegi, considered as the ancestor of the cultivated grapevine, is native from Eurasia. In Spain, natural populations of V. vinifera ssp. sylvestris can still be found along river banks. In this work, we have performed a wide search of wild grapevine populations in Spain and characterized the amount and distribution of their genetic diversity using 25 nuclear SSR loci. We have also analysed the possible coexistence in the natural habitat of wild grapevines with naturalized grapevine cultivars and rootstocks. In this way, phenotypic and genetic analyses identified 19% of the collected samples as derived from cultivated genotypes, being either naturalized cultivars or hybrid genotypes derived from spontaneous crosses between wild and cultivated grapevines. The genetic diversity of wild grapevine populations was similar than that observed in the cultivated group. The molecular analysis showed that cultivated germplasm and wild germplasm are genetically divergent with low level of introgression. Using a model‐based approach implemented in the software structure , we identified four genetic groups, with two of them fundamentally represented among cultivated genotypes and two among wild accessions. The analyses of genetic relationships between wild and cultivated grapevines could suggest a genetic contribution of wild accessions from Spain to current Western cultivars.     

Tracing the geographic origins of major avocado cultivars

It has been difficult to infer the genetic history of avocado breeding, owing to the role of hybridization in the origin of contemporary avocado cultivars. To address this difficulty, we used the model-based clustering program, STRUCTURE, and nucleotide polymorphism in 5960 bp of sequence from 4 nuclear loci to examine population structure in 21 wild avocado accessions. The origins of 33 cultivars were inferred relative to the wild sample. Nucleotide sequence diversity in domesticated avocados ranged between 80% and 90% of that observed for the same loci in wild avocado, depending on the diversity statistic used for comparison. Substantial genetic differentiation among 3 geographic groups of wild germplasm corresponded to the classically defined horticultural races of avocado. Previously undetected genetic differentiation was revealed in wild populations from Central Mexico, where 2 subpopulations were distinguished based on elevation and latitude.