Evaluation of genetic diversity in a Camelina sativa (L.) Crantz collection using microsatellite markers and biochemical traits

A genomic DNA library enriched with GA/TC repeats from Camelina sativa variety Calena has been analysed. After sequencing of about 200 randomly selected clones, approximately 60 % of them showed to contain simple or compound microsatellites with a high number of repeats. Among all microsatellite markers analysed 15 primer pairs amplified polymorphic fragments. Forty C. sativa accessions of different origin were genotyped with 15 microsatellite markers that generated 134 alleles with an average of 8.93 alleles per locus. The observed heterozygosity (Ho) among the accessions ranged from 0.0 to 0.15 with an average of 0.0370, whereas the average of expected heterozygosity (He) among accessions was 0.2769. The analysis of the average total heterozygosity (H_T = 0.651), the intrapopulation genetic diversity (H_S = 0.260), the interpopulation genetic diversity (D_ST = 0.391) and the coefficient of genetic differentiation among populations (G_ST = 0.574) demonstrated that 57.4 % of the genetic diversity is among the accessions, while 42.6 % resides within them. Phylogenetic tree of the 40 C. sativa accessions was constructed based on Nei’s genetic distance. The unweighted pair group method with arithmetic mean (UPGMA) dendrogram shows, except for CAM108 and CAM170, a clear discrimination among C. sativa accessions grouping them in five subgroups. ANOVA analysis indicates significant differences in some biochemical and agronomic parameters among the C. sativa accessions grouped according to Nei’s genetic distance. The result of the Tukey HSD test demonstrated that the A4 subgroup showed a significant higher TWS and linoleic acid (LA) content, while the subgroup A1 showed a significant higher linolenic and lower LA content compared to the remaining groups.     

Comparison of morphological traits and molecular markers to analyse diversity and structure of alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis> L.) cultivars

Diversity and structure of populations may differ substantially between morphological traits and molecular markers. Explanations of such discrepancies are crucial for further progress in breeding as well as for the maintenance of genetic resources. Our objective was to compare indices of among-cultivars differentiation for morphological traits (Q_ST) and molecular markers (F_ST) in alfalfa (Medicago sativa), a legume forage species. Ten cultivars representing the Northern and Southern types commonly grown in Europe were investigated. For each cultivar, 40 genotypes were analysed with 16 SSR markers and four morphological traits measured in two locations and several cuts. Q_ST values were in general high (0.02–0.39) compared to the differentiation observed with molecular markers (F_ST = 0.01), especially for growth habit, indicating that morphological traits were more efficient to structure the diversity than molecular markers. For morphological traits, a clear separation of Northern and Southern cultivars was observed, whereas for molecular markers, no clear structure was detected. Nevertheless, the grazing type cultivar Luzelle was separated from the rest of the cultivars for both morphological traits and molecular markers. Although pairwise differences between cultivars were significant for both morphological traits and molecular markers, the main part of the variation was found within cultivars. This large within-cultivar variation may be explained, besides the outcrossing reproductive mode and autotetraploid genetics, by the recent history of M. sativa domestication in Europe and the frequent seed exchanges. Selection for morphological traits (Q_ST > F_ST) was achieved without modification of within-cultivar neutral diversity.     

Genetic diversity of rhizobia associated with alfalfa in Serbian soils

We have evaluated the genetic diversity and phylogeny of alfalfa rhizobia, originating from different types of soils in Serbia and their ability to establish an effective symbiosis with alfalfa (Medicago sativa L.). A collection of 65 strains isolated from root nodules of alfalfa were characterized by rep-PCR analysis, partial and complete 16S rDNA gene and recA gene sequencing, as well as atpD gene sequencing and DNA–DNA hybridizations. The results of the sequence analyses revealed that Sinorhizobium meliloti is the dominant species in alfalfa nodules. Only one strain was identified as Sinorhizobium medicae, two strains as Rhizobium tibeticum and one strain as Rhizobium sp. Despite the fact that the majority of strains were identified as S. meliloti, a high genetic diversity at strain level was detected. Almost all isolates shared the ability to nodulate and fix nitrogen with M. sativa, except 11 of them, which were incapable of fixing nitrogen with this species. About 50% of the isolates showed values of symbiotic effectiveness (SE) above 50%, while 10% of the strains were highly effective with SE values above 70%. Some of the strains which were highly effective in nitrogen fixation at the same time could intensively solubilize phosphates, offering a possibility for multipurpose inoculum development. This was the first genetic study of rhizobia isolated from this region and also the first report of natural presence of R. tibeticum in root nodules of M. sativa.     

Multiple domestications of the Mesoamerican gene pool of lima bean (Phaseolus lunatus L.): evidence from chloroplast DNA sequences

The Mesoamerican (MA) gene pool of lima bean (Phaseolus lunatus L.) is widely distributed from northern Mexico to northern Argentina in its wild forms and from the southern United States to the east coast of Brazil in its domesticated forms. This broad distribution and lack of wild accessions of the MA gene pool in many areas of its natural distribution has impeded determining its center of domestication and establishing whether it has a single or multiple centers. To answer these questions, we evaluated 262 accessions of P. lunatus using two intergenic spacers of chloroplast DNA: atpB-rbcL and trnL-trnF. The data were analyzed using a maximum likelihood tree (ML), a haplotype network and two estimators of genetic differentiation (N _ST and G _ST). Nucleotide diversity (π) and haplotype (Hd) were quantified to estimate the percentage of reduction in genetic diversity (%r) as a founder effect. The ML tree and haplotype network indicated the existence of three groups (AI, MI and MII), which was supported by the high values of N _ST (0.61–0.80). Values for %r were high (58.67–60.83 %). Existence of Mesoamerican and Andean gene pools was confirmed, with two genetically and geographically distinct groups (MI and MII) within the MA gene pool. We present the first evidence for multiple origins of domestication for the MA gene pool. For MI, we propose western central Mexico as the domestication area and between Guatemala and Costa Rica for MII. We observed a founder effect in the MA gene pool as a result of domestication.     

Population differentiation and genetic variation inform translocation decisions for Liatris scariosa var. novae-angliae, a rare New England grassland perennial

Augmentation of small rare species populations is sometimes suggested on genetic grounds. However, outbreeding depression via dilution of local adaptation or break-up of genomic coadaptation may occur. These effects depend on the causes of population divergence. Here, we compare genetic measures of population divergence in Liatris scariosa var. novae-angliae, a rare New England perennial. We measured G_ST, neutral marker subdivision, and Q_ST, quantitative subdivision of propagule and juvenile plant traits. G_ST was relatively high. Q_ST for leaf shape exceeded G_ST, indicating local adaptation, while Q_ST for other traits fell within or below the G_ST range. Local adaptation appears low for juvenile traits, although the high G_ST cautions against translocation because of potential coadaptation. If translocation is still required, however, donor populations should contain high quantitative genetic diversity. We assess population size and allozyme diversity as predictors of quantitative genetic variation, but find these poor proxies for direct measurement.     

Preliminary study of genetic diversity in Swedish flax (Linum usitatissimum)

To investigate the genetic diversity of Linum usitatissimumL. in Sweden, 18 accessions, including 13 cultivars and five landraces, were analysed. This study was based on genetic variation in three enzyme systems (i.e., PGD, GPI and MDH) by using horizontal starch gel electrophoresis. The total genetic diversity of the studied flax material was very high (H _T= 0.62). Even though the highest genetic diversity lies within the accessions (G _ST= 0.07), a clear differentiation between fibre and oil flax was found with respect to three polymorphic loci (Pgd-1, Gpi-2 and Mdh-1). A phenogram, based on Nei's genetic distances between the accessions studied, showed five clearly defined groups but with low variation within the groups. The unexpected high genetic diversity found within accessions in the studied flax material may indicate that flax is more outbreeding than earlier believed.     

Rice genetic diversity at farm and village levels and genetic structure of local varieties reveal need for in situ conservation

Rice genetic diversity partitioning between farms, varieties and, within-variety diversity, were analysed in two villages of Maritime Guinea with contrasted agroecological conditions. One thousand and two hundred individual plants belonging to 45 accessions collected in eight farms were genotyped using 10 SSR markers. The molecular variance was evenly shared between and within accessions, while the farm effect was almost nil. Local varieties had a multi-line genetic structure. The number of multilocus genotypes was proportional to the utilisation rate of the variety in the village. The F _ST values between different accessions of each variety were significant which indicated low genetic consistency in the variety names. This varietal structure could mainly be explained by the migration phenomenon and the high varietal turnover. Compared to allelic diversity, multilocus genotypic diversity seemed to be the most suitable indicator of the quantitative distribution of diversity at different management scales (accession, farm and village). The within- and between-farm F _ST values were in the same order of magnitude. The within-farm diversity was not farm-specific but quantitatively high, i.e. up to 50% of the total genotypic diversity of a given village. Given the relative importance of the within-variety diversity, the in situ approach stands out as the most effective solution. As farms do not host specific diversity the in situ approach could be implemented by working with a small number of farms.     

Differentiation and distribution of indica and japonica rice varieties along the altitude gradients in Yunnan Province of China as revealed by InDel molecular markers

Indica–japonica variation represents the most significant genetic differentiation in Asian cultivated rice (Oryza sativa L. subsp. indica Kato or subsp. japonica Kato). Understanding the differentiation and distribution patterns of cultivated rice along altitude gradients will facilitate strategic utilization and conservation of rice germplasm from mountainous regions. In this study, we analyzed 203 varieties and 14 wild accessions of rice collected from localities across an altitude gradient between 450 and 2,350 m above sea level in Yunnan, China, applying the “InDel molecular index” developed recently. Results from PCA of the InDel data demonstrated significant genetic differentiation of rice varieties from Yunnan into indica and japonica types. A few cultivars and nearly all wild rice accessions showed only moderate or no differentiation. Further analyses demonstrated a clear distribution pattern of the rice varieties in the mountainous region: indica varieties were grown across the entire altitude gradient in the sampling areas, but most japonica varieties were found above 1,400 m. These results clearly indicated that indica rice could be cultivated in areas at much higher altitudes than those categorized by the traditional methods. The knowledge opens a new dimension for introducing indica rice varieties to mountainous regions at higher altitudes and for selecting rice germplasm in these regions. In addition, the pattern of significant indica–japonica differentiation in rice varieties from Yunnan suggested the exotic origin of cultivated rice, which did not support the hypothesis that Yunnan is a part of the center of origin of rice, although it is certainly one of the centers of genetic diversity for rice.     

Microsatellite analysis of genetic diversity and population genetic structure of <Emphasis Type="Italic">Aegilops tauschii</Emphasis> Coss. in Northern Iran

Genetic diversity and population genetic structure of Aegilops tauschii in Northern Iran were studied based on nine microsatellite loci. A high level of genetic diversity was observed from the accessions collected from six regions (provinces). These accessions include 79 samples of the two subspecies (tauschii and strangulata), the intermediate form (among morphologically distinguished subspecies) and ten accessions of Triticum aestivum. The nine microsatellites revealed a total of 141 alleles, with an average of 15.7 alleles per locus. A comparison of the parameters showing genetic diversity, including the observed heterozygosity (Ho), gene diversity (He) and Shannon’s information index (I) of Ae. tauschii accessions from different provinces in Northern Iran, indicated that subsp. tauschii possesses the highest genetic diversity, followed by intermediate form. Genetic distance between subsp. strangulata and subsp. tauschii was low, confirming high gene flow between these two subspecies. However, intermediate form was more distinct from both of them. It was also found that the genetic diversity of T. aestivum is obviously lower than that of Ae. tauschii accessions. Moreover, the level of genetic diversity for Gilan, Golestan and Mazanderan provinces was higher than for Ardebil, Ghazvin and Semnan provinces, suggesting that these regions may provide a readily available source of potentially useful variation for wheat improvement.     

Population genetic structure of in situ wild Sorghum bicolor in its Ethiopian center of origin based on SSR markers

In situ population studies of wild relatives of crops are crucial for the conservation of plant genetic resources, especially in regions with high genetic diversity and a risk of local extinction. Ethiopia is the center of origin for sorghum, yet little is known about the genetic structure of extant wild populations. Using 9 Simple Sequence Repeat loci, we characterized 19 wild populations from five regions, 8 local cultivar populations from three regions, and 10 wild sorghum accessions from several African countries. To our knowledge, this is the most comprehensive study to date of in situ wild sorghum populations in Africa. Genetic diversity corrected for sample size was significantly greater in the wild populations in situ than in local cultivars or the accessions. Approximately 41 % of the genetic variation in the wild plants was partitioned among populations, indicating a high degree of differentiation and potential value for germplasm conservation, and the average number of migrants (N_m) per generation was 0.43. Cluster analyses showed that some wild populations were grouped by geographic region, whereas others were not, presumably due to long-distance seed movement. Four wild populations from disjunct regions formed a unique cluster with an Ethiopian accession of subsp. drummondii and probably represent a weedy race. STRUCTURE and other analyses detected evidence for crop-wild hybridization, consistent with previous molecular marker studies in Kenya, Mali, and Cameroon. In summary, in situ wild sorghum populations in Ethiopia harbor substantial genetic diversity and differentiation, despite their close proximity to conspecific cultivars in this crop/wild/weedy complex.     

Genetic structure and history of Swiss maize (<Emphasis Type="Italic">Zea mays</Emphasis> L. ssp. <Emphasis Type="Italic">mays</Emphasis>) landraces

Between 1930 and 2003 with emphasis on the 1940s maize landraces (Zea mays L. ssp. mays) from all over Switzerland were collected for maintenance and further use in a new Swiss breeding program. The genetic relationship and diversity among these accessions stored in the Swiss gene bank is largely unknown. Our hypothesis was that due to the unique geographic, climatic, and cultural diversity in Switzerland a diverse population of maize landraces had developed over the past three centuries. The aims were to characterize the genetic diversity of the Swiss landraces and their genetic relationship with accessions from neighbouring regions as well as reviewing their history, collection, and maintenance. The characterization and grouping was based on analyses with ten microsatellite markers. Geographic, cultural, and climatic conditions explained a division in two distinct groups of accessions. One group consisted of landraces collected in the southern parts of Switzerland. This group was related to the Italian Orange Flints. The other group contained accessions from northern Switzerland which were related to Northern European Flints in particular German Flints. Historic evidence was found for a frequent exchange of landraces within the country resulting in a lack of region-specific or landrace-specific genetic groups. The relatively large separation between the accessions, indicated by high F _ST (0.42), might be explained partly by a bottleneck during the collection and maintenance phase as well as by geographical and cultural separation of north and south of the country. Due to the high genetic diversity, the accessions here are a potential resource for broadening the European flint pool.     

Molecular diversity, genetic structure and mating system of Calopogonium mucunoides Desv.

Calopogonium mucunoides Desv. is a species native of South and Central America that is used as green manure and a pasture crop. The molecular genetic diversity was characterized in 195 C. mucunoides accessions from a germplasm collection using 17 microsatellite markers. Outcrossing rate was estimated after the evaluation of six microsatellite loci in 200 genotypes originated from 10 open-pollinated progenies (20 genotypes per progeny). Six genetic clusters were identified in the germplasm collection by the STRUCTURE software analysis, neighbor-joining tree comparisons and principal component analysis, which highly correlated with the geographic locations where these accessions were originated or collected. These results were confirmed using AMOVA. The largest portion of the genetic variation was observed among clusters (64.38%). The results indicated that: multilocus outcrossing rate (t _m ) was 16.3%, suggesting a mixed mating system with a predominance of autogamy; single locus outcrossing rate (t _s ) was 11%; difference (t _m ?t _s ) was 0.054, indicating that only 5.4% of outcrossing occurred among related individuals; paternity correlation (r _p ) was 33% suggesting a low probability of finding full sibs among the progeny; parental coefficient of inbreeding (F _m ) was 5.0%, indicating a low degree of inbreeding in each parent. A core collection for C. mucunoides was assembled to capture the allelic diversity found in this study. The complete allelic diversity was represented by only 15 accessions. These results should be useful for exploiting the genetic resources of C. mucunoides and could influence future conservation efforts and breeding programs.     

Multivariate analysis of Prunus subgen. Cerasus germplasm in Iran using morphological variables

Knowledge of relationships among the cultivated and wild species of Cerasus, a subgenus of Prunus L., is important for recognizing gene pools, identifying pitfalls in germplasm collections and developing effective conservation and management strategies. In this study, morphological characterization of wild Cerasus subgenus species naturally growing in Iran, including P. avium L. (mazzard), P. mahaleb L., P. brachypetala Boiss., P. incana Pall., P. yazdiana Mozaff., P. microcarpa Boiss. subsp. microcarpa, P. microcarpa Boiss. subsp. diffusa and P. pseudoprostrata Pojark. and three commercial species, sweet cherry (P. avium L.), sour cherry (P. cerasus L.) and duke cherry (P. × gondouinii Rehd.) was investigated. Twenty-nine variables were recorded in 95 accessions of these species to detect similarities among them. All studied characteristics were showing a high degree of variability, but it was highly pronounced for plant height, leaf characters especially for dimensions and pubescence as well as for petiole and peduncle length. The majority of significant correlation coefficients were found in the characteristics representing plant size and growth habit with leaf size. Principal component analysis was performed for phenotypical diversity determination and grouping of species. Characters with high discriminating values were those related to growth habit, height, compactness, trunk diameter, leaf dimensions, petiole length, leaf tip and serration, flower color, peduncle length, fruit shape and stone shape. Based on the cluster analysis, species included in two main clusters, first those with large structure (sweet, sour and duke cherries, mazzard and mahaleb), second the other species with small structure which might be potentially suitable for rootstock breeding programs. Scatter plot using two first factors also confirmed the grouping by cluster analysis. The conservation of the highly diverse native populations of Iranian wild Cerasus species is recommended.     

Genetic diversity and structure of Ethiopian,Yemen and Brazilian C<Emphasis Type="Italic">offea arabica</Emphasis> L. accessions using microsatellites markers

Genetic diversity among 115 coffee accessions from the Coffea Germplasm Collection of IAC was assessed using SSR markers. The germplasm represents 73 accessions of Coffea arabica derived from spontaneous and subspontaneous plants in Ethiopia and Eritrea, species center of origin and diversity, 13 commercial cultivars of C. arabica developed by the Breeding Program of IAC, 1 accession of C. arabica cv. ‘Geisha’, 13 accessions of C. arabica from Yemen, 5 accessions of C. eugenioides, 4 accessions of C. racemosa and 6 accessions of C. canephora. Genetic analysis was performed using average number of alleles per locus (A), proportion of polymorphic loci (P), Shannon’s genetic index (H′ and G′_ST) and clustering analysis. All evaluated species were distinguished by a cluster analysis based on Jaccard’s coefficient. Differentiation between the cultivated plants of C. arabica and accessions derived from spontaneous and subspontaneous plants was observed. Spontaneous and subspontaneous accessions from Ethiopia were separated according to the geographical origin: east and west of the Great Rift Valley. Cultivated plants showed a low genetic diversity with a division in two groups: accessions from Yemen (H′=0,028) and Brazilian commercial cultivars (H′=0,030). The results agreed with previously reported narrow genetic basis of cultivated plants of C. arabica and supported the hypotheses about domestication of the species. This study also showed a significant genetic diversity among accessions from Ethiopia and Eritrea present in the Germplasm Collection of IAC. This diversity is specially observed in accessions from Sidamo (H′=0,143), Kaffa (H′=0,142) and Illubabor (H′=0,147) indicating their importance as source of genetic variability for coffee breeding programs.     

Assessment of phenotypic variation of Malus orientalis in the North Caucasus region

Malus orientalis Uglitzk. is the predominant Malus species of the Caucasian forests distributed in the north of Anatolia, Armenia, Russia as well as in Iran. It is considered as one of the probable minor ancestors of domestic apples. Although M. orientalis has a lower diversity of fruit quality, other valuable traits such as later blooming, adaptation to a wider array of habitats, and capacity for longer storage of the apples should be taken into account for improving the genetic makeup of the domestic apple. A joint expedition of scientists of the Julius Kühn-Institute from Germany and the Nikolaj I. Vavilov Research Institute of Plant Industry from Russia was performed into the North Caucasus region during August/September 2011. Altogether 101 M. orientalis accessions were collected from eight sites at the North Caucasus. Twenty-six traits such as size, color, shape, flavor and firmness of fruit and tree habit were used for phenotypic evaluation of the accessions. A high phenotypic diversity within the collected material of M. orientalis was indicated. Accessions characterized by suitable fruit traits like bigger size, larger cover color, less bitterness and better firmness as well as more sweetness and better flavor were found. However, small-sized flavorless fruits were also detected. Tree habit varied widely from upright to weeping. Subsequently, a comprehensive phenotypic and genetic evaluation of M. orientalis increases the knowledge of diversity, may provide new resources of agronomically important traits for breeding purposes, and gives support to determine accessions for a core collection.     

Genetic structure and differentiation among grapevines (<Emphasis Type="Italic">Vitis vinifera</Emphasis>) accessions from Maghreb region

Three gene pools representative of Vitis vinifera L. subsp. vinifera (=subsp. sativa Beger) growing in the Maghreb regions (North Africa) from Tunisia (44), Algeria (31) and Morocco (18) and 16 wild grape accessions (Vitis vinifera L. subsp. sylvestris (Gmelin) Beger) from Tunisia were analysed for genetic diversity and differentiation at twenty nuclear microsatellites markers distributed throughout the 19 grape chromosomes. 203 alleles with a mean number of 10.15 alleles per locus were observed in a total of 109 accessions. Genetic diversities were high in all populations with values ranging from 0.6775 (Moroccan cultivars) to 0.7254 (Tunisian cultivars). F _st pairwise values between cultivated grapevine populations were low but found to be significantly different from zero. High F _st pairwise values were shown between wild and cultivated compartments. Two parent offspring relationships, two synonyms and two clones of the same cultivar were detected. The rate of gene flow caused by vegetative dissemination of cultivated grapevine plants was not sufficient to genetically homogenise the pools of cultivars grown in different regions. The Neighbour Joining cluster analysis showed a clear separation according to geographical origins for the cultivated grapevines gene pools and revealed a high dissimilarity between cultivated and wild grapevine. However, three cultivars (Plant d’Ouchtata 1, Plant de Tabarka 3 and Plant d’Ouchtata 3) are very close to wild accessions and may result from a hybridisation between cultivated and wild accessions. The high level of differentiation between cultivated and wild accessions indicates that the cultivated accessions do not derive directly from local wild populations but could mostly correspond to imported materials introduced from others regions during historical times or derived from crossing between them.     

Genetic analysis of wheat (Triticum aestivum L.) and related species with SSR markers

Genetic diversity among 19 Triticum aestivum accessions and 73 accessions of closely related species was analyzed using simple sequence repeat (SSR) markers. Forty-four out of 497 SSR markers were polymorphic. In total 274 alleles were detected (mean 6.32 alleles per locus). The polymorphic information content (PIC) of the loci ranged from 0.3589 to 0.8854 (mean 0.7538). The D genome contained the highest mean number of alleles (6.32) followed by the A and B genomes (6.13 and 5.94, respectively). The correlation between PIC and allele number was significant in all genome groups (0.7540, 0.7361 and 0.7482 for A, B and D genomes, respectively). Among the seven homologous chromosome groups, genetic diversity was lowest in group 7 and highest in group 5. In cluster and principal component analyses, all accessions grouped according to their genomes were consistent with their taxonomic classification. Accessions with the A and D genomes were clustered into two distinct groups, and AABB accessions showed abundant genetic diversity and a close relationship. Triticum durum and T. turgidum were clustered together, consistent with their morphological similarity. Cluster analysis indicated emmer is closely related to hexaploid wheat. Compared with common wheat, higher genetic variation was detected in spelt, T. aestivum subsp. yunnanense and subsp. tibetanum. In addition, a close genetic relationship between T. polonicum and T. macha was observed. The results of the clustering and principal component analyses were essentially consistent, but the latter method more explicitly displayed the relationships among wheat and closely related species.     

Diversity analysis of Central Asia and Caucasian lentil (<Emphasis Type="Italic">Lens</Emphasis><Emphasis Type="Italic">culinaris</Emphasis> Medik.) germplasm using SSR fingerprinting

Diversity analysis was performed among 39 cultivated lentil (Lens culinaris Medik.) accessions of Central Asia and Caucasian origin using five highly polymorphic microsatellite markers. A total of 33 alleles determined ranging from 3 to 8 per locus. Estimated gene diversity value for 33 loci was 0.66. Genetic similarity indices among 39 accessions ranged from 0.24 to 1.0. Cluster analysis using the unweighted pair group method with arithmetic mean method classified accessions into six major groups at 0.5 similarity coefficient. More than half accessions from Tajikistan formed large cluster. On the other hand, a few accessions from each country showed unique genotypes. Overall, most of the accessions, except ones with closely related origin, were distinguished by the present high quality DNA fingerprinting. This molecular diversity information gives important basis for conservation strategy in gene bank and exotic germplasm introduction in breeding programs in Central Asia and Caucasian countries.     

A case study of seed exchange networks and gene flow for barley (Hordeum vulgare subsp. vulgare) in Morocco

Local patterns of seed regeneration and trade that occur outside the formal breeding sector (seed exchange networks) can have a strong influence on the genetic diversity and evolution of traditional crop varieties. Despite this, little is known about the extent to which seed exchange networks influence gene flow and genetic structure in traditional crop varieties. Here we study barley (Hordeum vulgare subsp. vulgare) in rural communes of Northern Morocco in 2008 and 2009. We quantified seed regeneration and exchange by farmers within the seed exchange network using structured interviews. Using SSR markers, we also quantified the neutral genetic diversity and structure of a complex of traditional varieties referred to as Beldi that is managed in this exchange network. The majority of farmers (>88 %) report cultivating Beldi. Most seeds of Beldi (70–90 %) are maintained on-farm, while the remainder of seeds are obtained from local markets within the commune. Beldi has high genetic diversity and there is weak but significant genetic structure between communes (F_ST = 0.031). From SSR marker data there is evidence of a high level of gene flow between communes not reported in interviews. Seeds purchased in local markets likely represent seeds from a larger geographic region, leading to lower genetic structure among communes than expected based on the reported level of on-farm seed regeneration and local sourcing of seed. We discuss the implications of this seed exchange network for the conservation of traditional barley varieties in the study region.     

Assessment of genetic variation in a working collection of Vigna vexillata (L.) A. Rich. by isozyme and RAPD analyses

Genetic variation based on isozyme and RAPD analyses was investigated in 47 and 34 accessions respectively of Vigna vexillata from different geographical origins and belonging to three botanical varieties. A total of 9 enzyme systems were studied, accounting for 14 putative loci, 8 of which were polymorphic. The analysis of genetic diversity revealed a low level of within accession variation (H_S=0.013), while between accession diversity (D_ST) was 0.120. Coefficient of gene differentiation (G_ST) was 0.905, indicating that most variation was among accessions. Nei's genetic distances were calculated on the basis of allelic frequencies and a UPGMA dendrogram was constructed. Twenty arbitrary 10-mer oligonucleotides were used in RAPD analysis. Amplification profiles disclosed a higher level of polymorphism than isozymes. Based on amplification patterns, the similarity index of Jaccard was calculated and a dendrogram constructed on the basis of the similarity matrix. The final clustering based on RAPD data was similar to the one obtained using isozyme allelic frequencies. The classification in botanical varieties did not reflect the allelic constitution of the different samples. On the other hand, referring to geographical origin, most accessions from Africa and from Latin America were distributed respectively in two distinct clusters in the dendrogram. This grouping might also reflect the differences observed in the germination behaviour of V. vexillata from the two continents.