Phenotypic Distance Research Articles

Predicting distances using a linear model: The case of varietal distinctness

Differences between plant varieties are based on phenotypic observations, which are both space and time consuming. Moreover, the phenotypic data result from the combined effects of genotype and environment. On the contrary, molecular data are easier to obtain and give a direct access to the genotype. In order to save experimental trials and to concentrate efforts on the relevant comparisons between varieties, the relationship between phenotypic and genetic distances is studied. It appears that the classical genetic distances based on molecular data are not appropriate for predicting phenotypic distances. In the linear model framework, we define a new pseudo genetic distance, which is a prediction of the phenotypic one. The distribution of this distance given the pseudo genetic distance is established. Statistical properties of the predicted distance are derived when the parameters of the model are either given or estimated. We finally apply these results to distinguishing between 144 maize lines. This case study is very satisfactory because the use of anonymous molecular markers (RFLP) leads to saving 29% of the trials with an acceptable error risk. These results need to be confirmed on other varieties and species and would certainly be improved by using genes coding for phenotypic traits.

The Relative Roles of Adaptation and Phylogeny in Determination of Larval Traits in Diversifying Anuran Lineages

I measured phenotypic traits important to the fitness of larval anurans to assess the relative roles of ancestral trait value and selective regime in determining present-day phenotypes. The positions of 14 species from three taxonomic families and three different habitats in a phenotypic space defined by 19 traits provided measures of taxonomic and ecological similarity. The distribution of phenotypic distances among species revealed that neither taxonomy nor habitat overwhelmingly determined phenotype. There appear to be multiple ways in which anurans can exploit pond types. However, the direction of phenotypic movement was not random from one species to the next. Independent contrasts revealed significant correlations in the evolution of traits that were consistent among lineages. These correlations reflected well-known trade-offs that result from functional relationships among the constituent traits. Although there is no simple pattern in the distribution of mean phenotypes across environments and lineages, the pattern of the evolutionary trajectories that created that distribution is consistent with a predictive theory of multivariate evolution.

An Imanishism-based Genetic Algorithm for Seeking Various Optimal Solutions of the Module Placement Problem

In order to find the plural number of optimal solutions for the module placement problem, which is of particular significance in the design of VLSI, a new Genetic Algorithm (GA) based on Imanishi's evolutionary theory is proposed. First of all, a phenotypic distance between two solutions, or individuals, is defined as the shortest Hamming distance between sets of isomorphic genotypes. If the phenotypic distance between two individuals is shorter than a threshold value, they are regarded as the same species. Then, a new generation alternation model that is analogous to the habitat segregation is presented. Since each individual in the population represents an isolating species, the diversity of the population is maintained spontaneously. Even though the selection of individuals based on their fitness is not employed, excellent individuals are created effectively by using the harmonic crossover operation combined with a local optimization method.

SPATIAL AND TEMPORAL GENETIC STRUCTURE OF WILD EMMER WHEAT IN JORDAN. I. PHENOTYPIC TRAITS

Natural populations of wild emmer wheat in Jordan represent a unique and sizable part of the species’ distribution in the Fertile Crescent. However, information on their genetic structure and diversity is limited. An understanding of the way genetic variation is partitioned among these populations is of primary importance for the ex situ sampling and in situ conservation of their genetic diversity. Fourteen categorical traits were used to characterize different phenotypes found in 12 wild emmer wheat populations in Jordan. They were scored in plants growing in 207 marked sampling sites and representing a wide range of observable variation. A strong effect of the heterogeneous habitats, encountered across collecting sites, was reflected in the magnitude and spatial distribution of phenotypic diversity. Several, and probably unique, first- and second-order associations among phenotypic traits reflect functional adaptation of the species to arid and semiarid Mediterranean environments. Phenotypic distances among populations were highly influenced by latitude and rainfall quotient (Q2) of collection sites. Spatial factors accounted for large portions (60.5–93.1%) of total variation in phenotypic diversity indices, suggesting strong provenance specificity. Temporal variation was less pronounced than spatial variation, and there were no drastic changes between years in frequencies of genotypes. Both spatial and temporal variation varied among populations.

Host-correlated morphological variation of Myzus persicae (Hemiptera: Aphididae) populations in Greece.

Morphological variation in nine characters of 157 clones of Myzus persicae (Sulzer) was examined by multivariate analysis. The clones were collected from peach, Prunus persica, the primary host and the secondary hosts tobacco, Nicotiana tabacum, cabbage, Brassica oleracea, sugarbeet, Beta vulgaris and pepper Capsicum annuum. The 156 clones originated from various regions of Greece, both in the north, where a large part of the population has an annual bisexual generation on peach, and in more southerly regions, where populations are predominantly unisexual. One clone was collected from tobacco in Caserta, Italy. All clones were laboratory-reared on potato. Canonical variate analysis, hierarchical cluster analysis and a non-parametric classification tree method both revealed morphological differences associated with the host-plant on which they were collected. The scores of the first two canonical variates separated the tobacco-feeding clones from those originating from other secondary host-plants. However, in tobacco-growing areas the tobacco-feeding form predominated in spring populations on peach, and was sometimes found on other secondary hosts. In addition, using cluster analysis, the clones from tobacco which were sampled in the most southeasterly region showed a relatively large phenotypic distance from those collected further north and west. Moreover, clonal phenotypes were affected both by host plant and by long-term parthenogenetic rearing. However, in spite of these effects, the tobacco form was generally distinguishable from aphids originating from other hosts, indicating that the difference must have a genetic basis. In separate analyses of the clones originating from secondary hosts no association was found between morphology and either life cycle category or colour. Discriminant analysis showed that 89% of 1723 specimens could be correctly classified into the two groups.

VNTR-based diversity analysis of 2x and 4x full-sib Musa hybrids

Summary of inheritance of maternal (AAB genome) and paternal (AA genome) VNTR amplification fragments in the full -sib 2x and 4x progeny populations. ____________________________________________________________________________ Maternal fragments Paternal fragments (Obino l’Ewai) (Calcutta 4) # % # % ____________________________________________________________________________ Diploid progeny Segregation 10 46 15 65 No segregation 8 36 3 13 Absent 4 18 5 22 Tetraploid progeny Segregation a 18 82 20 87 b No segregation 4 18 1 4 Absent 0 0 2 9 _________________________________________________________________________ ___ a segregation of 7 fragments solely due to absence of that fragment in TMPx 548 -9 b segregation of 1 fragment solely due to absence of that fragment in TMPx 548 -9 TMPx 7002-1 are most closely related to the maternal genotype (Obino l’Ewai). In cont rast, all the diploid hybrids form two groups associated at the 60% level of similarity, which are distinct from both parental genotypes (Figure 1). The major exceptions are TMPx 548 -9, which is separated at the 20% level of similarity from all other genotypes, tested and hybrid 5860-1 (4x) that is grouped with the diploid progeny. Hybrid 5860-1 (4x) was found to haveCalcutta 4 were very similar; 0.42 (±0.046) and 0.39775% similarity to TMP2x 1549 -5, both of which have 65% similarity to hybrid 1549-7 (2x) (Figure 1). This anomaly may be a consequence of hybr id 5860-1 (4x) possessing a high proportion of bi-allelic loci in common with these particular diploid full -sibs, as compared to multi -allelic loci of the other tetraploid hybrids. Clearly, this type of molecular marker analysis can not be used for inferring hybrid ploidy. Finally, TMP2x 1448 -1 and hybrid 1586 -2 (2x) appear particularly distinct from the majority of their 2x and 4x full -sib hybrids (Table 2). Both diploid and tetraploid hybrids had comparable mean levels of similarity to Calcutta 4 (32.2% and 34.3 %, respectively). However, tetraploid hybrids had more fragments in common with Obino l’Ewai than their diploid full-sibs (56.1% and 44.6%, respectively). This relationship was expected because the tetraploid hybrids have 75% of their genes donated by the maternal plantain 2n gametes (and the remaining 25% from the diploid banana), while their diploid full-sibs inherit 50% of their genes from each parent. The average phenotype of the tetraploid hybrids was also more closely related to Obino l’Ewai than Calcutta 4 (Table 3). The phenotypic distance between the tetraploid hybrids and Obino l’Ewai was 0.322 (±0.027), while the phenotypic distance between the tetraploid hybrids and Calcutta 4 was 0.470 (±0.021). Conversely, the phenotypic distance indic es for comparisons of diploid hybrids with Obino l’Ewai and (±0.043), respectively. This was expected based on the gametic contributions to diploid and tetraploid hybrids described above. For the relationship between hybrids and Obino l’Ewai, there was a significant association between the genetic similarity (based on VNTR) and the phenotypic resemblance (r = -0.546, P = 0.042). The linear relationship (R

Validating a core collection of Peruvian quinoa germplasm

A Peruvian quinoa core collection, containing 103 chosen ecotypes or landraces, was defined on a geographically stratified non-overlapping sampling procedure. The objective was to determine whether this protocol was correct. Hence, a phenotypic distance matrix among 76 accessions from this core collection was created by calculating the difference between each pair of accessions for each characteristic. These 76 accessions were chosen because they had complete data for eight morphological descriptors. The diversity index was calculated by averaging all the differences in the phenotypic value for each quantitative descriptor divided by the respective range, and considering a matching coefficient for the qualitative descriptors, i.e., 0 for characteristics that matched, and 1 if they did not. The total sum of squares from the analyses of variance for the phenotypic diversity index, based on morphological descriptors, was partitioned between and within Peruvian Departments. The between Department cluster variance was smaller (0.0022) than the within Department cluster variance (0.0144), because accessions with the same stem colour or similar inflorescence type and colour were grouped together irrespective of their Department. This was further corroborated by the average linkage cluster analysis, which was performed on the phenotypic diversity matrix to study the pattern of variation and the relationship between the quinoa landraces of this core subset according to their geographical origin. Within each sub-cluster (based on above qualitative descriptors) accessions were ranked by their Department of collection, which indicated that the sampling method was appropriate for choosing accessions for the Peruvian quinoa core collection.

Classification of African plantain landraces and banana cultivars using a phenotypic distance index of quantitative descriptors

Proper classification and establishment of relationships between and within Musa taxonomic clusters will be important tools for the genetic improvement of plantain and banana. This paper assesses the value of a phenotypic diversity index, based on 16 quantitative descriptors, for germplasm clustering and for identification of duplicates among 92 triploid plantain and banana accessions. Data were recorded during the plant and ratoon crops at Onne, a humid forest location in southeastern Nigeria. The phenotypic distance matrix was developed by calculating the average difference between each pair of accessions for all quantitative descriptors. Significant differences were observed for this phenotypic distance index between Musa taxonomic clusters. The between-cluster variance was larger (0.001779) than the within-cluster variance (0.001380). Wright’s φFS, which measures the overall diversity, was 0.5663. This value suggested little gene flow among triploid taxonomic clusters via pollen, which explains the higher population differentiation exhibited by this vegetatively propagated crop with very low male fertility. The results also suggested that variation observed within each Musa taxonomic cluster arose from mutations accumulated throughout the history of cultivation of this crop. Some putative duplicates based on qualitative descriptors were not regarded as the same accession according to the phenotypic diversity index based on quantitative descriptors. Hence, gene-bank curators should assess quantitative descriptors for the identification of duplicate accessions in Musa.

Population genetic differentiation of the great scallop Pecten maximus in western Britain investigated by randomly amplified polymorphic DNA

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 162:163-171 (1998) - doi:10.3354/meps162163 Population genetic differentiation of the great scallop Pecten maximus in western Britain investigated by randomly amplified polymorphic DNA D. A. Heipel1,*, J. D. D. Bishop2, A. R. Brand1, J. P. Thorpe1 1Port Erin Marine Laboratory, Isle of Man IM9 6JA, United Kingdom 2Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, United Kingdom *Present address: CEFAS Laboratory, Barrack Road, The Nothe, Weymouth, Dorset DT4 8UB, United Kingdom. E-mail: d.a.heipel@cefas.co.uk Randomly amplified polymorphic DNA (RAPD) banding patterns were compared between samples of the same year class of the scallop Pecten maximus (L.) from 5 locations (beds) within the commercial fishing grounds around the Isle of Man (UK). Phenotypic analysis of molecular variance (AMOVA) indicated that significant differentiation was present between these beds, although this accounted for only 2% of total variation, the remainder being between individuals within beds. As confirmed by multivariate analyses (PCOORD and UPGMA clustering), samples from the 2 northern Isle of Man beds resembled each other particularly closely, as did 2 southwestern beds, while the fifth, East Douglas, was relatively distinct. Comparison was extended to 2 samples taken outside the Irish Sea, from Mulroy Bay (Co. Donegal, Eire) and Plymouth (southwest England). Differentiation between the 3 regions was significant, accounting for 7% of total variation in a data set with balanced regional representation. A Mantel test on the whole data set revealed no significant correlation of phenotypic distance, based on RAPD banding pattern, with geographic distance. The potential correlation was largely destroyed by the marked differentiation of the population in Mulroy Bay, a semi-enclosed sea lough, and by the unexpectedly high phenotypic similarity between the Plymouth sample and the 2 northernmost Isle of Man samples. The RAPD data presented here provide the first evidence of population genetic structuring in exploited open-water stocks of this species, since previous allozyme studies of P. maximus have indicated genetic uniformity. Differentiation of the Mulroy Bay population from open-water stocks has been demonstrated previously in a study of mtDNA polymorphisms. Pecten maximus · Pectinidae · Scallops · RAPD · Population structure · Genetic differentiation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 162. Publication date: February 12, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Relationship between phenotypic and marker distances: theoretical and experimental investigations

Numerous studies have aimed at assessing the relationships between (i) distances computed from phenotypic data, (ii) distances computed from marker data and (iii) heterosis, for pairs of individuals or populations. The conflicting results obtained illustrate that these relationships are far from simple. In this paper, we investigate the effect on these relationships of (i) the polygenic inheritance of phenotypic traits and (ii) the structure of linkage disequilibrium between genetic markers and the loci involved in the variation of quantitative traits (QTLs). Both theoretical and experimental results showed that the relationship between marker distances and phenotypic distances computed from quantitative traits displays a triangular shape: low marker distances are systematically associated with low phenotypic distances, whereas high marker distances correspond to either low or high phenotypic distances. Because of this property, the linear coefficient of correlation between both distances decreases as the number of QTLs involved in the variation of the traits considered for phenotypic distance computation increases. Similar properties are expected for the relationship between heterosis and phenotypic distances.

Relationship between phenotypic and marker distances: theoretical and experimental investigations

Numerous studies have aimed at assessing the relationships between (i) distances computed from phenotypic data, (ii) distances computed from marker data and (iii) heterosis, for pairs of individuals or populations. The conflicting results obtained illustrate that these relationships are far from simple. In this paper, we investigate the effect on these relationships of (i) the polygenic inheritance of phenotypic traits and (ii) the structure of linkage disequilibrium between genetic markers and the loci involved in the variation of quantitative traits (QTLs). Both theoretical and experimental results showed that the relationship between marker distances and phenotypic distances computed from quantitative traits displays a triangular shape: low marker distances are systematically associated with low phenotypic distances, whereas high marker distances correspond to either low or high phenotypic distances. Because of this property, the linear coefficient of correlation between both distances decreases as the number of QTLs involved in the variation of the traits considered for phenotypic distance computation increases. Similar properties are expected for the relationship between heterosis and phenotypic distances.

Molecular Studies on Bromovirus Capsid Protein

Two members of the bromovirus group, brome mosaic virus (BMV) and cowpea chlorotic mottle virus (CCMV), selectively infect barley and cowpea, respectively, and also differ in their ability to systemically infect a common permissive host,Chenopodium quinoa.CCMV is confined to inoculated leaves ofC. quinoa,whereas BMV causes rapid systemic mottling. To examine whether host-specific determinants for systemic movement of BMV and CCMV in each of these hosts are localized in the coat protein (CP), sequences encoding this gene were exchanged between biologically active clones of BMV RNA3 (B3) and CCMV RNA3 (C3) to create chimera expressing heterologous CP genes (B3/CCP and C3/BCP). Inoculation of each chimera with its respective wild-type (wt) RNAs 1 and 2 to barley or cowpea orC. quinoaplants resulted in symptom phenotype and long distance movement characteristics similar to those of the parental virus donating RNAs 1 and 2. These observations suggest that neither BMV CP nor CCMV CP has host-specific determinants for long distance movement. Inoculation of additional recombinant viruses, constructed by reassorting wt genomic RNAs 1 and 2 of BMV and CCMV with either heterologous wt RNA3 (i.e., B1+B2+C3 and C1+C2+B3) or heterologous chimeric RNA3 (i.e., B1+B2+C3/BCP and C1+C2+B3/CCP), to susceptible hosts resulted only in localized infections. The significance of these observations in relation to bromovirus movement is discussed.

Emended description of Buttiauxella agrestis with recognition of six new species of Buttiauxella and two new species of Kluyvera: Buttiauxella ferragutiae sp. nov., Buttiauxella gaviniae sp. nov., Buttiauxella brennerae sp. nov., Buttiauxella izardii sp. nov., Buttiauxella noackiae sp. nov., Buttiauxella warmboldiae sp. nov., Kluyvera cochleae sp. nov., and Kluyvera georgiana sp. nov.

A total of 219 strains belonging to the genera Buttiauxella and Kluyvera were studied; 171 of these strains were isolated from mollusks, mainly snails and slugs, obtained from around the world. On the basis of DNA-DNA hybridization data, the strains were grouped into 11 genomospecies. A total of 44 phenotypic characters were used to differentiate the genera Buttiauxella and Kluyvera at the genus level and to identify genomospecies. There were significantly higher phenotypic probability distances between the genomospecies in the genus Battiauxella and the genomospecies in the genus Kluyvera than between the genomospecies in the same genus. Therefore, the existence of Buttiauxella and Kluyvera as different genera was confirmed. The existence of new species necessitated broadening the definitions of both genera. In two cases, Buttiauxella species could not be quantitatively differentiated biochemically, and several other pairs of species could be separated only by the results of one biochemical test. Nonetheless, combinations of several characteristics were used in differentiate all of the species with levels of certainly ranging from log 10.79 to log 57.77 (calculated as probability distances). The following new species are proposed: Buttiauxella ferragutiae (type strain, ATCC 51602 [DSM 9390]), Buttiauxella gaviniae (type strain, ATCC 51604 [DSM 9393]), Buttiauxella brennerae (type strain, ATCC 51605 [DSM 9396]), Buttiauxella izardii (type strain, ATCC 51606 [DSM 9397]), Buttiauxella noackiae (type strain, ATCC 51607 [DSM 9401]), Buttiauxella warmboldiae (type strain, ATCC 51608 [DSM 9404]), Kluyvera cochleae (type strain, ATCC 51609 [DSM 9406]), and Kluyvera georgiana (type strain, ATCC 51603 [DSM 9409]).

Patterns of Meristic Variation among Parthenogenetic Teiid Lizards (Genus Cnemidophorus) of the Yucatan Peninsula and Their Progenitor Species, C. angusticeps and C. deppei

Patterns of Meristic Variation among Parthenogenetic Teiid Lizards (Genus Cnemidophorus) of the Yucatan Peninsula and Their Progenitor Species, C. angusticeps and C. deppei

A comparison between allozyme data and phenotypic distances from defensive secretion in Oreina leaf‐beetles (Chrysomelinae)

AbstractThe genetic relationships between five Oreina species (Chrysomelidae, Coleoptera) were studied. Of these species, four (O. bifrons, O. gloriosa, O. speciosa, O. variabilis) feed on Apiaceae and secrete mixtures of autogenous cardenolides from defensive glands, whilst the other (O. speciosissima) feeds on Asteraceae and is able both to produce cardenolides and to sequester pyrrolizidines N‐oxides (PAs). A dendrogram based on the different mixtures of cardenolides produced by the different species agreed with these genetic relationships. In other words, cardenolide mixtures are good taxonomic markers, since the clustering method based on chemical defense produces a branching pattern similar to that based on genetic relationships.

Variability for isozyme, vegetative compatibility and RAPD markers in natural populations of Phomopsis subordinaria

Phomopsis subordinaria is a common fungal pathogen which attacks the scapes of Plantago lanceolata in natural populations. Three classes of genetic markers (isozymes, vegetative compatibility (VC) and random amplified polymorphic DNAs (RAPDs)) were tested for their suitability to reveal polymorphisms among isolates of P. subordinaria , originating from 27 locations in the Netherlands and 7 locations in other western European countries. Enzyme electrophoresis failed to show any variation in P. subordinaria . No polymorphisms were found with seven enzymes in 69 isolates originating from 23 locations. Enzyme electrophoresis is, therefore, not a suitable method to identify individual isolates of this species. In contrast, VC tests and RAPDs revealed substantial variation. With VC tests 89 VC groups (VCGs) were found among 134 isolates from 34 locations. Four RAPD primers could distinguish between 15 RAPD groups among 47 isolates from 8 locations. Similarity coefficients were calculated using 18 RAPD characters. These values revealed a high genetic resemblance among the 15 RAPD groups. Shannon-Weaver indexes, based on the VC and RAPD data, were calculated for three locations. Two locations proved to be significantly more diverse than the third. Our study suggests that vegetative compatibility and RAPDs are two independent methods which can be helpful tools for research projects on evolutionary relationships and on genetic structure in fungal populations. The VC test is a sensitive method to find variation in P. subordinaria , but RAPD analysis can be used to calculate phenotypic distances.

Population differentiation decreases with depth in deep-sea gastropods

The evolutionary processes that have generated the rich and highly endemic deep-sea benthic invertebrate fauna remain largely unstudied. Patterns of geographic variation constitute the most basic and essential information for understanding speciation and adaptive radiation. Here we present a multivariate analysis of phenotypic distance to quantify geographic variation in shell form among populations of eight deep-sea gastropod species distributed along a depth gradient in the western North Atlantic. Our primary aim is to identify regions within the deep sea that may promote population differentiation. The degree of interpopulation divergence is highest at the shelf-slope transition (200 m), and then decreases dramatically with increasing depth across the bathyal region (200–4000 m) to the abyssal plain (>4000 m). Phenotypic change parallels faunal change along the depth gradient, suggesting that the selective regime becomes more uniform with increasing depth. Results indicate that the potential for gastropod radiation within the deep-sea environment (>200 m) varies geographically and is highest in the narrow upper bathyal region.

Population structure of the Jirels: Patterns of mate choice

The influence of mating practices on genetic structure has been an area of great interest for anthropologists. In this paper, the techniques of potential mates analysis are employed to explore the mating patterns observed among the Jirels, a tribal population of eastern Nepal. Genealogical, anthropometric, dermatoglyphic, and demographic data for members of seven Jirel villages are used. Potential mate pools for a sample of 268 females are enumerated by village. Age structure and the Jirel restriction against clan endogamy are found to severely limit the number of males who are potential mates for a given female. The mating structure of the population is illuminated by statistical analysis of the characteristics of 160 actual mate pairs and all corresponding potential mate pairs. Using this approach several general mate choice practices were verified: 1) biological kin tend to be avoided as mates, 2) members of the same clan are excluded as potential mates, 3) mate exchange between clans is nonrandom, 4) individuals similar in age tend to be selected as mates, and 5) mates are drawn from the natal village more often than random expectation. A multivariate phenotypic distance measure between individuals did not reveal any evidence for assortative mating for either anthropometric or dermatoglyphic characters.

Comparison of Isozyme and Virulence Diversity Patterns in the Bean Rust FungusUromyces appendiculatus

(...) Thirteen enzymes, representing 15 phenotypic markers, were found suitable for this purpose. Phenotypic diversity as detected by the 15 isozyme markers and virulence on 18 differential bean lines were compared for 27 geographically diverse isolates. Greater diversity was found for virulences than for isozymes. No relationship between geographic and phenotypic distance was found. Three phenotypic clusters based on virulence and isozyme data were identified by cluster analysis. The data support the hypothesis that U. appendiculatus is not a homogeneous species and also suggest that urediospores may occasionally fertilize pycnia in nature

Variation and covariation in Vicia faba L. populations of Mediterranean origins

Variation and covariation in 15 Vicia faba L. ssp. major populations from Italy. Greece and Egypt were analyzed. Ten quantitative morphobiological characters of agronomical and nutritional interest were observed. Differences among countries of origin were highly significant for all characters except for lowest podded node. Phenotypic distances among populations, both within and among origins, estimated on canonical variates evidenced that the Egyptian populations from a distinct group and that a relevant degree of similarity exists among the Greek and the Italian meterial. The covariation structure within populations, which was studied by means of factor analysis, was comparatively simpler in the Egyptian material than in that form the other two Mediterranean countries. The differences evidenced can be attributed to different gene associations between characters and suggest the possibility of obtaining, through recombination, genotypes agronomically more favorable.