Study of genetic variation in sesame (Sesamum indicum L.) using agro-morphological traits and ISSR markers

This research was conducted to study the genetic variation among eighteen genotypes of sesame (Sesamum indicum L.) collected from various agro-climatic regions of Iran along with six exotic genotypes from the Asian countries using both agro-morphological and ISSR marker traits. The results showed significant differences among genotypes for all agro-morphological traits and a relatively high genetic coefficient of variation observed for number of fruiting branches per plant, capsules per plant, plant height and seed yield per plant. Cluster analysis based on these traits grouped the genotypes into five separate clusters. Larger inter- than intra cluster distances implies the presence of higher genetic variability between the genotypes of different groups. Genotypes of two clusters with a good amount of genetic divergence and desirable agronomic traits were detected as promising genotypes for hybridization programs. The 13 ISSR primers chosen for molecular analysis revealed 170 bands, of which 130 (76.47%) were polymorphic. The generated dendrogram based on ISSR profiles divided the genotypes into seven groups. A principal coordinate analysis confirmed the results of clustering. The agro-morphological traits and ISSR markers reflected different aspects of genetic variation among the genotypes as revealed by a non significant cophenetic correlation in the Mantel test. Therefore the complementary application of both types of information is recommended to maximize the efficiency of sesame breeding programs. The discordance among diversity patterns and geographical distribution of genotypes found in this investigation implies that the parental lines for hybridization should be selected based on genetic diversity rather than the geographical distribution.     

Genetic variation and clonal diversity of <Emphasis Type="Italic">Bromus ircutensis</Emphasis> Kom. in the Otingdag sandy land detected by <Emphasis Type="Italic">ISSR markers</Emphasis>

Genetic variation and clonal diversity of nine populations of Bromus ircutensis Kom. from the Otingdag sandy land were investigated using Inter Simple Sequence Repeat (ISSR) markers. A total of 102 bands were amplified by using 11 ISSR primers chosen for the study. Among those 99% were polymorphic indicating high level of genetic variation at the species level with a mean genetic diversity (H) of 0.292 and Shannon information index (I) of 0.450. Percentage of polymorphic loci (PPL) of nine populations was 76.48% on average, which provides more evidence of considerable genetic variation at the population level. AMOVA analysis revealed that total genetic variation was higher within populations (87.06%) than between populations (12.94%), which is mainly the result of the extensive gene flow (Nm = 1.682) among B. ircutensis populations. UPGMA cluster analysis divided the nine populations into two groups. There was significant or moderate negative correlations between genetic diversity parameters (PPL, H, I) and longitude or latitude. Mantel test also showed a significant correlation between geographical distance and genetic distance (r = 0.681, p = 0.002). Our findings indicated that distribution of B. ircutensis populations was influenced by geographical and ecological factors. Clonal diversity was also high with 108 individuals identified by 11 ISSR primers being all of different genets. Our results provide a molecular basis for sustainable management and conservation of B. ircutensis in the study area.     

Molecular characterization of <Emphasis Type="Italic">Vigna radiata</Emphasis> (L.) Wilczek genotypes based on nuclear ribosomal DNA and RAPD polymorphism

Mungbean germplasm characterization, evaluation and improvement are fundamentally based on morpho-agronomic traits. The lack of break-through in mungbean production has been due to non-availability of genetic variability for high yield potential. Forty-four genotypes of mungbean [Vigna radiata (L.)Wilczek] were subjected to random amplified polymorphic DNA (RAPD) analysis to assess the genetic diversity and relationships among the genotypes. Multilocus genotyping by twelve RAPD primers generated 166 markers and detected an average of intraspecific variation amounting to 82% polymorphism in banding patterns. Dendrogram obtained from cluster analysis delineated all the 44 genotypes into six clusters. Higher values of Nei’s gene diversity (h) and Shannon information index (i) and genetic distance analysis validate existence of wide genetic diversity among mungbean genotypes tested. Besides internal transcribed spacer (ITS) length variations, single nucleotide polymorphisms (SNPs) and insertions/deletions (INDELS) were detected at number of sites in nuclear rDNA region and the sequences of representatives of each sub-cluster and all distinct genotypes have been submitted to NCBI database and assigned Gen accession numbers HQ 148136-148147. Multiple sequence alignment revealed further lineages of distinct genotypes with main RAPD clusters. The measures of relative genetic distances among the genotypes of mungbean did not completely correlate the geographical places of their development. The homogeneous phenotypic markers proved insufficient in exhibiting genetic divergence among mungbean genotypes studied. RMG-62, RMG-976, and NDM-56 have been identified as potential source of parents for crop improvement. RAPD primers, OPA-9 and OPA-2 as polymorphic genetic markers and number of pods/plant and number of seeds/plant as dependable phenotypic markers have been identified for improving yield potentials. This genetic diversity will be of significance in developing intraspecific crosses in mungbean crop improvement programme.     

Population structure and genetic diversity of wild <Emphasis Type="Italic">Helianthus</Emphasis> species from Mozambique

The production of sunflower suffered a major decline in Mozambique after its independence in 1975. Civil war, human activities and environmental damage subjected the species to an ecological stress contributing to reduce the number and size of wild populations. As this reduction is often related to a loss of genetic variation we estimated the genetic diversity within and among populations of wild Helianthus from five districts of Mozambique using RAPD markers. The 44 accessions studied grouped into four major clusters exhibiting structured variability with regard to geographic origin. A high level of genetic diversity (He = 0.350 and I = 0.527) was retained at the population level. The genetic variation among populations was high (59.7%), which is consistent with low gene flow (Nm = 0.338). The proportion of total genetic diversity residing among these populations should be kept in mind to devise different conservation strategies in order to preserve these populations. Currently wild Helianthus genetic resources present in Maputo and Sofala are on the edge of extinction mainly due to excessive urbanization. Therefore, conservation of what remains of this plant genetic diversity is essential for sustainable utilization and can be useful for breeding programs.     

Patterns of subspecies genetic diversity among oilseed <Emphasis Type="Italic">Brassica rapa</Emphasis> as revealed by agro-morphological traits and SSR markers

Brassica rapa (2n = 20, AA genome) is an important oil yielding species of the family Brassicaceae and characterized by wide range of genetic and morphological subtypes suitable for cultivation under diverse agro-climatic regions of India. In this study, genetic diversity among three subspecies of B. rapa including yellow sarson, toria and outlier brown sarson was estimated using various agro-morphological traits and simple sequence repeat (SSR) markers. Maximum variability was recorded for siliqua angle (Coefficient of variation = 30.9%), followed by seeds/siliqua (CV = 18.8%), leaf length (CV = 10%) and plant height (CV = 16.8%). Principal component analysis explained more than 50% of the total observed morphological variability for first two components. Of the 107 SSR markers tested, 80 generated reproducible, clear and distinct amplicons of which, 65 (81.25%) were found polymorphic. The number of alleles at each locus ranged from 2 to 7, with an average of 3.03 alleles per marker. A total of 197 alleles were detected at 65 SSR loci with average PIC value of 0.457 and a mean resolving power of 3.04. Neighbor-Joining cluster analysis based on morphological traits and SSR markers separately classified all the 28 genotypes into five major groups. The population structure analysis resulted into three sub-populations with certain extent of admixture among the earlier established taxonomic sub-groups. Twenty-three unique alleles were detected in thirteen B. rapa varieties. The clustering analysis and principal coordinate analysis outlined the genetic relationships among different varieties belonging to the three subspecies of B. rapa. Genetically diverse genotypes as illustrated by score plots and from the clustering patterns brought out the wide range of diversity present among B. rapa genotypes and the underlying options available for selecting parental genotypes for hybridization and developing high yielding cultivars suitable for Indian conditions.     

Transgressive segregation of primary and secondary metabolites in F<Subscript>2</Subscript> hybrids between <Emphasis Type="Italic">Jacobaea aquatica</Emphasis> and <Emphasis Type="Italic">J. vulgaris</Emphasis>

Hybridization between plant species can have a number of biological consequences; interspecific hybridization has been tied to speciation events, biological invasions, and diversification at the level of genes, metabolites, and phenotypes. This study aims to provide evidence of transgressive segregation in the expression of primary and secondary metabolites in hybrids between Jacobaea vulgaris and J. aquaticus using an NMR-based metabolomic profiling approach. A number of F₂ hybrid genotypes exhibited metabolomic profiles that were outside the range encompassed by parental species. Expression of a number of primary and secondary metabolites, including jacaronone analogues, chlorogenic acid, sucrose, glucose, malic acid, and two amino acids was extreme in some F₂ hybrid genotypes compared to parental genotypes, and citric acid was expressed in highest concentrations in J. vulgaris. Metabolomic profiling based on NMR is a useful tool for quantifying genetically controlled differences between major primary and secondary metabolites among plant genotypes. Interspecific plant hybrids in general, and specifically hybrids between J. vulgaris and J. aquatica, will be useful for disentangling the ecological role of suites of primary and secondary metabolites in plants, because interspecific hybridization generates extreme metabolomic diversity compared to that normally observed between parental genotypes.     

A comparative map viewer integrating genetic maps for <Emphasis Type="Italic">Brassica</Emphasis> and <Emphasis Type="Italic">Arabidopsis</Emphasis>

Background  

Molecular genetic maps provide a means to link heritable traits with underlying genome sequence variation. Several genetic maps have been constructed for Brassica species, yet to date, there has been no simple means to compare this information or to associate mapped traits with the genome sequence of the related model plant, Arabidopsis.     

Analysis of genetic diversity among medicinal therapist <Emphasis Type="Italic">Trigonella foenum</Emphasis>-<Emphasis Type="Italic">graecum</Emphasis> L. genotypes through RAPD and SSR markers

Trigonella is recognized as a medicinal therapist throughout the globe due to its multifaceted rare medicinal properties. It is indigenous from Iran to Northern India but has gained global acceptance towards cultivation and consumption for its yellow-to-amber colored seed which substantially contributes to food, pharmaceutical, nutraceutical and cosmetic industry. Genetic diversity serves as an excellent tool for developing improved crop varieties with breeder preferred traits. Unfortunately, very little information available on variability existing in commercial Trigonella genotypes considerably impedes the crop improvement. In this study, ninety Trigonella genotypes belonging to most productive North Indian states were subjected to multilocus genotyping using RAPD (49) and SSR (13) primers and detected an average of 55.60 and 50.16% polymorphism, respectively. The percentage polymorphism range (RAPD, 16.7–90.90; SSR, 33.30–66.66) average band informativeness (RAPD, 0.182–0.85; SSR, 0.21–0.91) and resolving power (RAPD, 0.95–9.984; SSR, 1.68–7.28) obtained revealed the wide range of diversity prevailing among these genotypes. Hierarchical clustering of genotypes in nine different clusters showed Trigonella’s genetic variability has wide genetic distribution across different agro-climatic zones. No consistency was observed while grouping Trigonella varieties based on eco-geographical region. Eventually, knowledge of these genetic differences significantly contributes in designing intra-specific crosses with potential interest to spice breeding programs. To the best of our knowledge, this is the first report of genetic diversity using SSR molecular markers in Trigonella foenum-graecum L.     

Genetic Variability in Pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) Estimated by Morphological Data and Amplified Fragment Length Polymorphism Markers

Data on genetic similarity among crop cultivars is of vital importance for the plant breeder. The objectives of this study were to group pepper (Capsicum annuum L.) genotypes into clusters according to their distances as estimated by morphological traits and amplified fragment length polymorphism (AFLP) markers and to assess the relationships between the two. Thirty-nine pepper genotypes obtained from different countries were grown in the greenhouse at University of the Free State, South Africa, during 2001 and 2002 in a randomized complete block design with three replications. A total of 20 different morphological traits were measured and six AFLP primer pairs were used to estimate pairwise genetic distances. Both datasets showed high genetic distances among the different genotypes, indicating high genetic diversity among them. The mean genetic distance among Ethiopian pungent elongated-fruit genotypes, was lower than that between them and the introduced ones. Morphological and AFLP distance estimations generally clustered together genotypes with similar fruit sizes. Significant, positive correlation was observed between morphological and AFLP diversity estimations. The narrow genetic basis among the Ethiopian pungent elongated-fruit cultivars suggests that the pepper breeding program of Ethiopia should focus on enriching its germplasm through local collection and introductions from other parts of the world.     

Genetic variation of wild litchi (<Emphasis Type="Italic">Litchi chinensis</Emphasis> Sonn. subsp. <Emphasis Type="Italic">chinensis</Emphasis>) revealed by microsatellites

Understanding the amount and distribution of genetic diversity in natural populations can inform the conservation strategy for the species in question. In this study, genetic variation at eight nuclear microsatellite loci was used to investigate genetic diversity and population structure of wild litchi (Litchi chinensis Sonn. subsp. chinensis). Totally 215 individuals were sampled, representing nine populations of wild litchi. All eight loci were polymorphic, with a total of 51 alleles. The expected heterozygosity in the nine populations ranged from 0.367 to 0.638 with an average value of 0.526. Inbreeding within wild litchi populations was indicated by a strong heterozygote defect. Significant bottleneck events were detected in the populations from Yunnan and Vietnam, which could be responsible for lower levels of genetic diversity in these populations. Measures of genetic differentiation (F _ST = 0.269) indicated strong differentiation among wild litchi populations. Significant correlation was found between genetic differentiation and geographical distance (r = 0.655, P = 0.002), indicating a strong isolation by distance in these populations. Bayesian clustering suggested genetic separation among three regional groups, namely, the western group, the central group and the eastern group. Some conservation strategies for wild litchi populations were also proposed based on our results.     

Genetic diversity and population structure assessment of Chinese <Emphasis Type="Italic">Senna obtusifolia</Emphasis> L. by molecular markers and morphological traits of seed

Senna obtusifolia L. is an important medicinal plant in Asia. This study was the first report on the genetic diversity and population structure of S. obtusifolia which were collected from 47 geographic populations widespread in China. Inter-Simple Sequence Repeat (ISSR) and Start Codon Target Polymorphism (SCoT) combined with seeds morphological traits were used to investigate the relationship of 47 populations. 11 ISSR primers yielded 98 polymorphic bands with 81.67% polymorphism. 24 SCoT primers yielded 267 polymorphic bands with 89.59% polymorphism. The number of allele (Na), the number of effective allele (Ne), Nei’s diversity index (H), and Shannon’s information index (I) reflected a high level of genetic diversity of S. obtusifolia species. The greatest genetic distance (G _D) existed between Southwest and Northwest (0.4022_ISSR/0.5019_SCoT), while the Eastern and Northern showed the least genetic distance (0.1751_ISSR/0.2186_SCoT). The genetic differentiation (Gst) was 0.4875_ISSR/0.4434_SCoT, and the gene flow (Nm) was 0.5256_ISSR/0.6275_SCoT, which indicated that gene exchange among four regions was limited. 47 samples were divided into four clusters mainly according to their geographic distribution through clustering and structure analysis. The analysis on the combined data of ISSR and SCoT showed more reliable and superior results than single analysis of ISSR and SCoT. This study explored the effectiveness of ISSR and SCoT markers to evaluate the genetic diversity and population structure of S. obtusifolia and provided useful information for S. obtusifolia germplasm research and breeding program.     

Genetic diversity following demographic recovery in the insular endemic plant <Emphasis Type="Italic">Galium catalinense</Emphasis> subspecies <Emphasis Type="Italic">acrispum</Emphasis>

Galium catalinense (Rubiaceae) is a perennial shrub consisting of two subspecies endemic to California’s Channel Islands: Galium catalinense subsp. catalinense on Santa Catalina Island, and G. catalinense subsp. acrispum, a state-endangered taxon on San Clemente Island. A long history of overgrazing by introduced herbivores has contributed to population declines in G. catalinense subsp. acrispum. We surveyed 12 populations throughout the taxon’s range for genetic variation using eight polymorphic microsatellite loci to determine the genetic impact of this demographic bottleneck. At the taxon level, 65 alleles were identified with an average of 8.1 alleles per locus, although many alleles were rare; the effective number of alleles per locus averaged 2.6. Expected heterozygosity was 0.550. Individual populations had between six and eight polymorphic loci, with expected heterozygosities ranging from 0.36 to 0.60, and effective numbers of alleles ranging from 1.8 to 3.5 per locus. Populations fell into three or four genetic clusters, depending on type of analysis, which may represent refugia where the populations persisted during intense herbivory. There is little evidence of genetic bottlenecks or substantial inbreeding within populations. These findings, coupled with indications of recent migration between populations, suggest that G. catalinense subsp. acrispum is currently unlikely to be endangered by genetic factors, but small population sizes make the taxon vulnerable to future loss of genetic diversity. Management strategies based on these genetic data, population sizes, and the spatial distribution of populations are discussed.     

Hybridization between <Emphasis Type="Italic">Schoenoplectus</Emphasis> sedges across Chesapeake Bay marshes

Hybridization is an evolutionary mechanism capable of enhancing adaptive potential, especially among species in fragmented or disturbed ecosystems like coastal marshes. In this study, we evaluated whether hybridization might influence adaptive responses in coastal marshes that are susceptible to the effects of global environmental change. To do so, we examined the extent and nature of hybridization between Schoenoplectus americanus and S. pungens, two ecologically dominant sedges in low-lying marshes across Chesapeake Bay (USA). Observed patterns of variation at genetically based morphological traits, cpDNA and nuclear microsatellite markers confirm that introgressive hybridization occurs between the two species. Comparisons of microsatellite and cpDNA profiles found that hybridization is reciprocal, although a disproportionate number of hybrids exhibit genomic asymmetries favoring S. americanus. AIC model selection consistently identified latitude as the strongest explanatory variable for the distribution of parental species, although discriminant analysis indicated that distributions also correspond to variation in environmental conditions. Discriminant analysis further indicated that ecological correlates of hybrid and S. americanus genotypes are similar, but not uniformly so. These findings indicate that the boundary between S. americanus and S. pungens is porous, and that hybridization could influence responses of one or both species to changing environmental regimes.     

Population genetic structure of the endangered and endemic medicinal plant <Emphasis Type="Italic">Commiphora</Emphasis><Emphasis Type="Italic">wightii</Emphasis>

Commiphora wightii is a medicinally important endangered species endemic to the Thar Desert of Rajasthan, India and adjoining areas of Pakistan. The populations of this species are declining sharply because of its extensive use as a natural herb. Random amplified polymorphic DNA analysis was conducted to find the genetic variation among 7 populations of C. wightii. Of the 100 random primers screened, 44 primers yielded 220 loci. Statistical analysis indicated low genetic diversity (H _pop = 0.0958; I = 0.1498; mean polymorphic loci = 14.28%), and high genetic differentiation among the populations (G _ST = 0.3990; AMOVA Φ _ST of 0.3390; Bayesian θ ^(II) = 0.3002). The low genetic diversity may be due to geographic isolation and restricted gene flow (N _m = 0.7533) between the fragmented populations. Unsustainable utilization of the plant has fragmented the population continuum which served the purpose of genetic exchange between populations. Mantel’s test was performed which revealed a highly significant positive correlation between genetic and geographic distance (r ² = 0.614, P = 0.023) among the populations studied. Low variation can also be attributed to poor seed setting and the slow growth pattern of the species, which is also an apomict. In UPGMA dendrogram the Commiphora wightii samples were divided into two major and one minor cluster. These findings can serve as a guide to preserving the genetic resources of this medicinal plant species.     

Nuclear genetic variation of <Emphasis Type="Italic">Rosa odorata</Emphasis> var. <Emphasis Type="Italic">gigantea</Emphasis> (Rosaceae): population structure and conservation implications

Rosa odorata var. gigantea is one of the most important ancestors of modern roses, which owns many merit traits including large flower, early flowering, and tea scent. Due to habitat loss and fragmentation, it has been listed as a rare and endangered species in China. In this study, a total of 424 accessions from 27 locations across its major distribution range were sampled. Its genetic diversity and population structure were assessed using a combination of seven nuclear microsatellite markers and one single-copy nuclear gene. Moderate to high within-population genetic diversity and moderate differentiation among populations were revealed despite its narrow distribution. The sampled 27 populations were resolved into two genetic clusters with limited contemporary and historical gene flows. The Red River Fault Zone was inferred to be a physical or geographical barrier to gene flow between these two genetic clusters. Genetic distances were significantly associated with geographic distances, indicating the isolation-by-distance model. Our ecological niche modeling indicated that R. odorata var. gigantea had high current potential areas in the central Yunnan province and substantial losses of high potential distribution areas in the western Yunnan in the future. Two detected clusters showed significant genetic differentiation and represented two separate evolutionary lineages, which should be recognized as two evolutionary significant units (ESUs) for conservation concerns. These results could be applied for the decision-making and conservation planning for this important species.     

Mapping quantitative trait loci for important agronomic traits in finger millet (<Emphasis Type="Italic">Eleusine coracana</Emphasis>) mini core collection with genomic and genic SSR markers

Allele identification for agro-morphological traits and stress resistance is a major concern across the globe for improving productivity of finger millet. Here, we used 46 genomic and 58 genic simple sequence repeats (SSRs) markers in a set of 66 accessions used to constitute a global mini-core collection for analysing their genetic structure as a population and establishing association among markers and twenty morphological traits including resistance to finger blast. Phenotypic data revealed a wide range of variation for all traits except flag leaf width and flag leaf sheath width. We got amplification of 81 alleles by the 31 genomic SSRs at an average of 2.61 alleles per locus. Polymorphism information content (PIC) values varied from 0.21 to 0.75 and average gene diversity was 0.49. Structure analysis of the population using the genomic SSR data divided the accessions into two clusters where Indian and exotic accessions were grouped in separate clusters. Genic SSRs which were associated with blast resistance genes, amplified 36 alleles at an average of 2 alleles per locus. PIC values ranged from 0.32 to 0.37 and average gene diversity was 0.45. Population structure analysis using data from these SSRs grouped the accessions into three clusters, which broadly correspond to their reaction to blast disease. Twenty-two significant associations were found using the GLM approach for 20 agro-morphological traits both in 2012 and 2014, while, 7 and 5 significant marker-trait associations were identified using MLM in 2012 and 2014 respectively. The SSR markers FMBLEST35 and FMBLEST36 designed from the Pi21 gene sequence of rice were found to be associated with blast disease resistance in finger millet indicating that the gene homologues play a significant role in an important role for neck blast resistance.     

Fitness consequences of infection of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> with its natural bacterial pathogen <Emphasis Type="Italic">Pseudomonas viridiflava</Emphasis>

Variation in plant resistance to pathogen infection is commonly observed in interactions between wild plants and their foliar pathogens. Models of host–pathogen interactions indicate that a large cost of infection is generally necessary to maintain this variation, yet there is limited evidence that foliar pathogens cause detectable fitness reductions in wild host plants. Most published work has focused on fungal pathogens. Pseudomonas viridiflava, a common bacterial pathogen of the annual weed Arabidopsis thaliana across its range, comprises two distinct genetic clades that cause disease symptoms of different severity. Here we measured the extent of infection of wild A. thaliana populations in the Midwest, USA, and examined the effect on seed production, in field and growth-chamber experiments, of experimental inoculation with isolates from the two clades. We found infection with P. viridiflava varied from 0 to 56% in Midwest A. thaliana populations, with the possibility of several leaves per plant infected later in the growing season. In the growth chambers, experimental inoculation reduced seed set by averages of 15 and 11% for clades A and B, respectively. In the field experiment, only clade A affected plant fitness significantly, reducing seed set by an average of 38%. Underlying these average effects we observed both negative and positive effects of infection, and variation in both fitness among plant genotypes and sensitivity to environmental conditions.     

Genetic determinism of reproductive fitness traits under drought stress in the model legume <Emphasis Type="Italic">Medicago truncatula</Emphasis>

Fitness traits that determine the reproductive ability of individuals and the persistence of populations are affected by drought stress. Medicago truncatula that commonly encounters drought stress in its natural area, and for which large natural diversity and genetic tools are available, is a suitable species to investigate genetic determinism of fitness traits under stress. In a common garden, three successive cycles of short drought stress were applied after flowering, during the reproductive stage that is the most susceptible to drought for that species. Ten genotypes derived from natural populations and a mapping population were used to investigate the genetic determinism of vegetative and reproductive traits as components of fitness. A large genetic variation was observed and transgressive genotypes (more resistant or more susceptible than the parental genotypes) were found in the mapping population. Fitness traits were reduced by 5–74% in drought condition compared to well-watered condition. The most affected characters were total pod number per plant and total pod weight per plant. A total of 49 QTL, explaining between 6 and 38% of phenotypic variation for vegetative and reproductive fitness traits, were detected on all chromosomes except chromosome 6. A major QTL for flowering date (R ² of 19 and 38%) that co-located with QTL for reproductive fitness traits were found on chromosome 7. In this study, no major QTL specific to drought-stressed or well-watered conditions were detected. We, thus, showed that QTL explaining fitness traits were numerous with small effects, in accordance with the genetic determinism of a complex trait.     

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

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