Inter-simple sequence repeat (ISSR) variation in forest coffee trees (Coffea arabica L.) populations from Ethiopia

Genetic variation of forest coffee trees (Coffea arabica L.) from four regions of Ethiopia was investigated using inter-simple sequence repeat (ISSR) markers. A total of 160 individuals representing 16 populations were sampled. Eleven ISSR primers amplified a total of 123 fragments of which 31 fragments (25%) were polymorphic. Estimate of total gene diversity (H _T), and the coefficient of genetic differentiation (G _ST) were 0.37 and 0.81, respectively. This indicates that most of the variability is between populations than within populations. The partitioning of genetic variation into within and between populations based on Shannon’s information index also revealed more differentiation between populations (0.80) than within populations (0.20). In the phenogram most of the coffee tree samples were clustered on the basis of their regions of origin but failed to cluster according to their respective populations, which could be attributed to the presence of substantial gene flow between adjacent populations in each region assisted by man in the process of transplantation or by wild animals such as monkeys, which eat the berries and defecate the seeds elsewhere. On the other hand, the inter-regional clustering of some coffee tree samples from Bale and Jimma regions could be due to the transport of coffee seeds across regions and their subsequent planting. Although ISSR markers detected lower polymorphic loci than previously reported results with random amplified polymorphic DNA (RAPD) markers on the same materials, it can be used as an alternative method for molecular characterization of C. arabica populations. The results may provide information to select sites for in situ conservation.     

Genetic relationship among wild,landraces and cultivars of hazelnut (Corylus avellana) from Portugal revealed through ISSR and AFLP markers

The genus Corylus, a member of the birch family Betulaceae, includes several species that are widely distributed throughout temperate regions of the Northern Hemisphere. This study assesses the genetic diversity in 26 international cultivars and 32 accessions of Corylus avellana L. from Portugal: 13 wild genotypes and 19 landraces. The genetic relationships among the 58 hazelnuts (Corylus avellana L.) were analyzed using inter simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP) markers. Eighteen ISSR primers and seven AFLP primer pairs generated a total of 570 unambiguous and repeatable bands, respectively, from which 541 (95.03 %) were polymorphic for both markers. Genetic similarity index values ranged from 0.239 for wild types and cultivars to 0.143 for landraces and wild types. The genetic relationships were presented as a Neighbor-Joining method dendrogram and a two-dimensional principal coordinate analysis (PCoA) plot. The Neighbor-Joining dendrogram showed three main clusters, and the PCoA analysis has shown to be congruent with the hierarchical analysis. Bayesian analysis clustered all individuals into three groups showing a good separation among wild genotypes, landraces and cultivars. The genetic diversity found on wild genotypes and Portuguese landraces may provide relevant information for the diversity conservation and it will be useful in breeding programs and to identify local selections for preservation.     

Effects of forest management on mating patterns,pollen flow and intergenerational transfer of genetic diversity in wild Arabica coffee (Coffea arabica L.) from Afromontane rainforests

Coffea arabica, the wild ancestor of all commercial Arabica coffee cultivars worldwide, is endemic to the montane rainforests of Ethiopia. These forests, which harbour the most important C. arabica gene pool, are threatened by increasing anthropogenic disturbance, potentially altering the mating patterns, pollen dispersal and maintenance of genetic diversity in C. arabica understorey populations. We genotyped 376 adult coffee shrubs and 418 progenies from three natural unmanaged, and three highly managed coffee populations, using 24 microsatellite markers. Mating system analysis of C. arabica yielded an overall multilocus outcrossing rate of 76%, which contrasts with the common knowledge that C. arabica is a predominantly selfing species. In highly managed coffee populations, paternity could be assigned to 78% of the progenies, whereas in the unmanaged natural coffee populations, only 57% of the progenies could be assigned to a father, indicating reduced long‐distance pollen dispersal in managed forests. Furthermore, the fraction of selfed progenies was significantly higher in managed (23%) than unmanaged (10%) coffee forests. Finally, the lack of spatial genetic structure in all studied populations suggests high seed dispersal in unmanaged populations, and intense berry harvesting and coffee planting in the managed populations. Our results imply that in situ conservation of the wild gene pool of C. arabica must focus on limiting intensification of coffee forest management, as decreased pollen dispersal and increased selfing in C. arabica in intensively managed populations may increase the risk of genetic erosion. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 76–88.     

Detection of genetic diversity and selective gene introgression in coffee using RAPD markers

RAPD (randomly amplified polymorphic DNA) markers generated by arbitary decamers have been successfully employed to detect genetic polymorphisms between coffee species and between Coffea arabica genotypes. The RAPD profiles were used to construct dendrograms and these were consistent with the known history and evolution of Coffea arabica. Material originating from Ethiopia and the arabica sub-groups — C. arabica var. typica and C. arabica var. bourbon — were clearly distinguished. RAPD analysis therefore reflects morphological differences between the sub-groups and the geographical origin of the coffee material. Species-specific amplification products were also identified, but, more importantly, amplification products specific to C. canephora were identified in two C. arabica genotypes, Rume Sudan and Catimor 5175. This diagnostic product is therefore indicative of interspecific gene flow in coffee and has biological implications for selective introgressive hybridisation in coffee. Our study demonstrates the power of the polymerase chain reaction technology for the generation of genetic markers for long-lived perennial tree and bush crops.On study leave from: Universidad de San Carlos de Guatemala, Facultad de Agronomia, Ciudad Universitaria, Zona 12, Apartado Postal No. 1545, Guatemala, Central America     

Molecular characterisation of wild populations and landraces of common bean from northwestern Argentina

Abstract

Information on the variability of wild bean populations and landraces is essential to set conservation strategies and design breeding programmes aimed at enlarging the genetic base of commercial beans. Nineteen Argentinean common bean landraces and wild populations were characterised and their diversity was analysed by means of inter‐simple sequence repeat (ISSR) markers and seed proteins. Populations were successfully identified as belonging to the Andean gene pool of origin by phaseolin electrophoresis, whereas ISSR markers revealed high levels of inter‐ and intra‐population variability. Four of 10 primers produced polymorphic and reproducible DNA profiles, which were used to generate UPGMA (unweighted pair group method with arithmetical averages) and NJ (neighbour‐joining) trees. ISSR markers revealed a high level of variability both within wild bean populations and landraces. Genetic variability of wild samples was associated with their geographic distribution. By contrast, landraces were clustered, at least to some degree, based on their seed colour and shape, showing no clear discrimination among sites. The results presented here suggest that, to a certain extent, hybridisation between wild beans and landraces occurs in the wild, a hypothesis that needs to be tested through further analyses.     

Analysis of genetic structure in a sample of coffee (Coffea arabica L.) using fluorescent SSR markers

The knowledge of population structure is important to determine the degree of linkage disequilibrium, which allows the selection of genotypes for association mapping. Using 47 SSR markers, the genetic variability and population structure of 68 accessions of C. arabica (wild and cultivated) and of three diploid species used as reference were evaluated. The analysis was done with the distance method and the structure model. The structure analysis inferred nine subpopulations (k = 9), for which the greatest values of probability were obtained. Three of the groups corresponded to the three diploid species as expected. There were six groups identified within C. arabica. The genetic subdivisions within C. arabica were based on geographical origin, degree of domestication, and dispersal history of coffee. One group consisted entirely of cultivated genotypes, where intense population bottleneck were associated with a founder effect. This was the most homogeneous group, as demonstrated by the reduced distance between cultivars in the dendrogram. Three of the cultivated genotypes, originating from Sudan, were separated into an independent group, presumably due to selective adaptation to a different set of environmental conditions. Another group consisted of genotypes of the type “ennarea” that were grown and cultivated in isolation on the shores of the Tana lake. The semi-wild genotypes clustered into three different groups. This type of analysis provides a strong evidence of population structure in C. arabica. Based on these findings, it is possible to better identify a balanced sample of diverse plants in germplasm.     

Population structure,morphological and genetic diversity within and among melon (Cucumis melo L.) landraces in Iran

ISSR markers were applied to evaluate the genetic diversity and differentiation of 270 individuals of 27 Iranian C. melo landraces of various varietal groups include vars. inodorous, cantalupensis, reticulatus, ameri, dudaim. Genetic diversity among the studied genotypes obtained by GeneAlex analysis (H?=?0.08, I?=?0.12, Na?=?0.77, PPL?=?22.6%). Cluster analysis divided Iranian melon landraces into two main cluster. Non-sweet genotype (dudaim group) was well separated from sweet genotypes (inodorous, ameri, reticulatus, cantalupensis). The most similar genotypes were BANI and TONI (0.95) and the most dissimilar ones were GER and TS (0.58). AMOVA result showed that the percentage of genetic variation among and within Iranian melon is 69% and 31%, respectively. All landraces evaluated based on 10 morphological traits which revealed the diversity of melon varietal groups. Bayesian analysis assigned ten landraces to Pop 1, eight landraces to Pop 2 and nine melon landraces to Pop 3. Bayesian and UPGMA cluster analyses demonstrated the almost related results. Our results indicated that ISSR markers technique alongside polyacrylamide gel analysis could be helpful to discriminate varieties of melon.     

Assessment of Genetic Diversity in Ziziphus mauritiana Using Inter-Simple Sequence Repeat Markers

Genetic diversity among 47 ber accessions belonging to cultivated species (Ziziphus mauritiana Lam) and one wild accession of Ziziphus nummularia (Burm F) Willed was investigated using Inter-Simple Sequence Repeat (ISSR) markers. A total of 167 amplification products were detected with 18 ISSR primers of which 152 (89.96%) were polymorphic. Most of the primers that produced distinct bands (14 primers out of 18) contained dinucleotide repeats. Primers based on (AC)n and (AG)_n repeats produced more polymorphic bands. Genetic similarity ranging from 43.07% to 90.30% suggested that the 48 Ziziphus genotypes used in the study were divergent. Cluster analysis based on UPGMA method and Bootstrap analysis separated all the 48 genotypes in four distinct clusters. The present study has successfully distinguished morphologically similar genotypes that emphasize the use of molecular markers to the taxonomists. Morphologically similar but genetically distinct genotypes, identified using ISSR markers could be potential sources for genotype identification and to resolve controversies over misnomination of ber genotypes. Present study is the first report on the exploitation of ISSR markers in ber for genetic diversity analysis.     

Genetic mapping of a new race specific resistance allele effective to Puccinia hordei at the Rph9/Rph12locus on chromosome 5HL in barley

Background

Tea is one of the most popular beverages in the world. Many species in the Thea section of the Camellia genus can be processed for drinking and have been domesticated. However, few investigations have focused on the genetic consequence of domestication and geographic origin of landraces on tea plants using credible wild and planted populations of a single species. Here, C. taliensis provides us with a unique opportunity to explore these issues.

Results

Fourteen nuclear microsatellite loci were employed to determine the genetic diversity and domestication origin of C. taliensis, which were represented by 587 individuals from 25 wild, planted and recently domesticated populations. C. taliensis showed a moderate high level of overall genetic diversity. The greater reduction of genetic diversity and stronger genetic drift were detected in the wild group than in the recently domesticated group, indicating the loss of genetic diversity of wild populations due to overexploitation and habitat fragmentation. Instead of the endangered wild trees, recently domesticated individuals were used to compare with the planted trees for detecting the genetic consequence of domestication. A little and non-significant reduction in genetic diversity was found during domestication. The long life cycle, selection for leaf traits and gene flow between populations will delay the emergence of bottleneck in planted trees. Both phylogenetic and assignment analyses suggested that planted trees may have been domesticated from the adjacent central forest of western Yunnan and dispersed artificially to distant places.

Conclusions

This study contributes to the knowledge about levels and distribution of genetic diversity of C. taliensis and provides new insights into genetic consequence of domestication and geographic origin of planted trees of this species. As an endemic tea source plant, wild, planted and recently domesticated C. taliensis trees should all be protected for their unique genetic characteristics, which are valuable for tea breeding.     

Genetic diversity within and among the wild populations of Murraya koenigii (L.) Spreng., as revealed by ISSR analysis

Murraya koenigii (L.) Spreng., commonly known as curry leaf plant, is found in the different hilly regions of India. In the present study, fifty-nine accessions representing eight wild populations of M. koenigii were analyzed using thirteen ISSR primers. A total of 152 bands were amplified, out of which, 136 were polymorphic corresponding to 89.47% polymorphism across the accessions. The pairwise population genetic distances were calculated for all the populations that varied from 0.05 to 0.13 between the populations of M. koenigii. AMOVA and Nei’s genetic diversity analysis revealed higher genetic variations within populations than among the populations. The clustering of populations in the dendrogram was not in congruence with geographical affiliations. The results indicate that the ISSR method is sufficiently informative and powerful to estimate the genetic diversity in M. koenigii populations. As M. koenigii is an important wild plant genetic resource, therefore, information on genetic variability might be a potential source as breeding material for development of commercially valuable traits in M. koenigii plants.     

Exploring Germplasm Diversity to Understand the Domestication Process in Cicer spp. Using SNP and DArT Markers

To estimate genetic diversity within and between 10 interfertile Cicer species (94 genotypes) from the primary, secondary and tertiary gene pool, we analysed 5,257 DArT markers and 651 KASPar SNP markers. Based on successful allele calling in the tertiary gene pool, 2,763 DArT and 624 SNP markers that are polymorphic between genotypes from the gene pools were analyzed further. STRUCTURE analyses were consistent with 3 cultivated populations, representing kabuli, desi and pea-shaped seed types, with substantial admixture among these groups, while two wild populations were observed using DArT markers. AMOVA was used to partition variance among hierarchical sets of landraces and wild species at both the geographical and species level, with 61% of the variation found between species, and 39% within species. Molecular variance among the wild species was high (39%) compared to the variation present in cultivated material (10%). Observed heterozygosity was higher in wild species than the cultivated species for each linkage group. Our results support the Fertile Crescent both as the center of domestication and diversification of chickpea. The collection used in the present study covers all the three regions of historical chickpea cultivation, with the highest diversity in the Fertile Crescent region. Shared alleles between different gene pools suggest the possibility of gene flow among these species or incomplete lineage sorting and could indicate complicated patterns of divergence and fusion of wild chickpea taxa in the past.     

iPBS-Retrotransposons-based genetic diversity and relationship among wild annual Cicer species

Lack of requisite genetic variation in cultivated species has necessitated systematic collection, documentation and evaluation of wild Cicer species for use in chickpea variety improvement programs. Cicer arietinum has very narrow genetic variation, and the use of a wild relative in chickpea breeding could provide a good opportunity for increasing the available genetic variation of cultivated chickpea. Genetic diversity and the relationship of 71 accessions, from the core area of chickpea origin and domestication (Southeastern Turkey), belonging to five wild annual species and one cultivated species (Cicer arietinum) were analysed using iPBS-retrotransposon and ISSR markers. A total of 136 scorable bands were detected using 10 ISSR primers among 71 accessions belonging to 6 species, out of which 135 were polymorphic (99.3 %), with an average of 13.5 polymorphic fragments per primer, whereas iPBS detected 130 bands with 100 % polymorphism with an average of 13.0 bands per primer. C. echinospermum and C. pinnatifidum were the most diverse among species, whereas C. arietinum exhibited lower polymorphism. The average polymorphism information contents (PIC) value for both marker systems was 0.91. The clustering of the accessions and species within groups was almost similar, when iPBS and ISSR NeighborNet (NNet) planar graphs were compared. Further detailed studies are indispensable in order to collect Cicer germplasm, especially C. reticulatum, from southeastern Turkey particularly, from Karacada? Mountain for preservation, management of this species, and to study their genetic diversity at molecular level. This study also demonstrates the utility and role of iPBS-retrotransposons, a dominant and ubiquitous part of eukaryotic genomes, for diversity studies in wild chickpea and in cultivated chickpea.     

Molecular analysis of introgressive breeding in coffee (Coffea arabica L.)

Nineteen arabica coffee introgression lines (BC₁F₄) and two accessions derived from a spontaneous interspecific cross (i.e. Timor Hybrid) between Coffea arabica (2n=4x=44) and C. canephora (2n=2x=22) were analysed for the introgression of C. canephora genetic material. The Timor Hybrid-derived genotypes were evaluated by AFLP, using 42 different primer combinations, and compared to 23 accessions of C. arabica and 8 accessions of C. canephora. A total of 1062 polymorphic fragments were scored among the 52 accessions analysed. One hundred and seventy-eight markers consisting of 109 additional bands (i.e. introgressed markers) and 69 missing bands distinguished the group composed of the Timor Hybrid-derived genotypes from the accessions of C. arabica. AFLP therefore seemed to be an extremely efficient technique for DNA marker generation in coffee as well as for the detection of introgression in C. arabica. The genetic diversity observed in the Timor Hybrid-derived genotypes appeared to be approximately double that in C. arabica. Although representing only a small proportion of the genetic diversity available in C. canephora, the Timor Hybrid obviously constitutes a considerable source of genetic diversity for arabica breeding. Analysis of genetic relationships among the Timor Hybrid-derived genotypes suggested that introgression was not restricted to chromosome substitution but also involved chromosome recombinations. Furthermore, the Timor Hybrid-derived genotypes varied considerably in the number of AFLP markers attributable to introgression. In this way, the introgressed markers identified in the analysed arabica coffee introgressed genotypes were estimated to represent from 9% to 29% of the C. canephora genome. Nevertheless, the amount of alien genetic material in the introgression arabica lines remains substantial and should justify the development of adapted breeding strategies. Received: 2 February 1999 / Accepted: 12 May 1999     

Arbitrarily primed-PCR based diversity assessment reflects hierarchical groupings of Indian tetraploid wheat genotypes

Genetic diversity analysis using PCR with arbitrary decamer primers (RAPD — random amplified polymorphic DNA) was carried out in a set of 63 tetraploid wheat genotypes which comprised 24 durum landraces, 18 durum cultivars, nine dicoccum cultivars, ten less commonly cultivated species and two wild tetraploid species. The durum and dicoccum wheat genotypes are a part of the germplasm used in Indian tetraploid wheat breeding programs. A total of 206 amplification products were obtained with 21 informative primers, of which 162 were polymorphic. The highest degree of polymorphism was seen in the wild and less commonly cultivated species (68.9%). Durum released cultivars showed greater polymorphism (50.6%) than landraces (44.8%), while dicoccum cultivars showed a considerably low level of polymorphism (23.6%). Cluster analysis led to the separation of wild and cultivated genotypes, and among cultivated emmer wheat distinct groups were formed by the durum cultivars, durum landraces and dicoccum cultivars. The subgroupings of landraces had no relation to their geographical distribution. The durum cultivars formed subgroups based on common parentage in their pedigree. Among species, wild timopheevi wheat (T. araraticum) and its cultivated form (T. timopheevi) formed a distinct group distant from all other genotypes. The present study is a first attempt at determining the genetic variation in Indian tetraploid wheats at the molecular level. Received: 10 January 1999 / Accepted: 30 January 1999     

Genetic diversity of <Emphasis Type="Italic">Vitis vinifera</Emphasis> L. in Azerbaijan

To examine the genetic diversity of Vitis vinifera L., growing in the region near the Caspian Sea of Azerbaijan Republic, nuclear genomes of 31 cultivated and 34 wild grapevine accessions were studied at population and individual levels using five ISSR primers. In total, 51 fragments were amplified, of which 45 were found to be polymorphic. A high level of polymorphism was revealed (the mean PPF and PIC values constituted 87.69% and 0.94, respectively). High values of the EMR, MI, and RP indices showed the effectiveness of the application of ISSR primers and the possibility of their use in further investigations in this direction. Cluster analysis based on Nei’s genetic distance values showed that all genotypes could be grouped into seven main clusters. Furthermore, no differences between the wild and cultivated grape wine accessions were revealed. For instance, there was no distinct distribution of the accessions according to their geographical localization. On the basis of the PIC values, the group of cultivars from Absheron Peninsula was distinguished by the highest polymorphism level (PIC = 0.36). Natural populations from the Guba and Shabran regions were characterized by a relatively low polymorphism level (PIC = 0.31 and PIC = 0.28, respectively), and a wild population from Nabran demonstrated the lowest polymorphism level (PIC = 0.25). The data obtained confirmed paleontological and historical data of different periods and provided the supposition that Azerbaijan was the center of diversity of V. vinifera L. In addition, our data indicate that Azerbaijan grape landraces originated from local wild forms.     

Genetic characterization of Iranian safflower (Carthamus tinctorius) using inter simple sequence repeats (ISSR) markers

Safflower (Carthamus tinctorious L.) is valued as a source of high quality vegetable oil. 20 ISSR primers were used to assess the genetic diversity of 18 accessions of safflower collected from different geographical regions of Iran. The ISSR primers combinations revealed 57.6 % polymorphism, among 338 genetic loci amplified from the accessions. The sum of effective number of alleles and observed number of alleles were 29.76 and 36.77, respectively. To understand genetic relationships among these cultivars, Jacquards’ similarity coefficient and UPGMA clustering algorithm were applied to the ISSR marker data set. ISSR markers grouped accessions into two main clusters and four sub clusters. Also, the principal coordinate analysis (PCoA) supported the cluster analysis results. The results showed these genotypes have high genetic diversity, and can be used for alternative safflower breeding program.     

Genetic variation and cultivar identification in Cymbidium ensifolium

As a popular flowering species with many cultivars, Cymbidium ensifolium (L.) is commercially important in horticulture. However, so far little has been known about genetic diversity and conservation genetics of this species. Understanding of the genetic variation and relationships in cultivars of C.?ensifolium is a prerequisite for development of future germplasm conservation and cultivar improvement. Here we report assessment of genetic variations in C.?ensifolium cultivars using the DNA fingerprinting technique of inter-simple sequence repeats (ISSR). A total of 239 ISSR loci were identified and used for evaluation of genetic variation with a selection of 19 ISSR primers. Among these ISSR loci, 99.16% were polymorphic with wide genetic variation as shown by Nei??s gene diversity (H?=?0.2431) among 85 tested cultivars. ISSR fingerprinting profiles showed that each cultivar had its characteristic DNA pattern, indicating unequivocal cultivar identification at molecular level. Eighteen cultivar-specific ISSR markers were identified in seven cultivars. The cultivar Sijiwenhan was confirmed as hybrid by four ISSR primers. Several cultivars with same name but different geographical origins were distinguished based on their ISSR profiles. A dendrogram generated with ISSR markers could group 73 of 85 cultivars into four major clusters. Further analysis of ISSR variation revealed that about 69% of total genetic variation in this species is due to genetic divergence inside geographical groups. Our results suggest that both germplasm collection and in?situ conservation are important for future planning of C.?ensifolium species conservation.     

Genotypic diversity and structure of Satureja mutica revealed by inter-simple sequence repeat markers

Satureja mutica (Lamiaceae) is an herbaceous medicinal plant which grows in Iran. The objective of the study was to obtain an overview of the genetic relatedness among and within seven populations of this species using inter-simple sequence repeat (ISSR). Fourteen ISSR primers amplified a total of 197 DNA fragments of which 176 (88.91%) were polymorphic. All ISSR primers were highly effective in discriminating among the populations. Genetic similarity coefficients ranged from 0.45 to 0.94, indicating considerable distance and diversity in the germplasm and were confirmed by clustering analysis. The dendrogram showed a clear clustering pattern of plants indicating a significant association between genetic similarity and geographical distance. Analysis of molecular variance revealed that a greater proportion of total genetic variation existed within populations (75%) rather than among populations (25%). The study indicated that ISSR markers were effective and reliable for assessing the degree of genetic variation of S. mutica. These findings can support future research on the selection of S. mutica for breeding and medicinal plant development.     

Patterns of genetic variation of the genusCapsicum (Solanaceae) in Mexico

The evolutionary relationships of 186 accessions ofCapsicum from Mexico were studied through enzyme electrophoresis. A total of 76 alleles representing 20 genetic loci coding for nine enzyme systems were observed and the allelic variations of enzymes were studied for geographical distribution. Allele frequencies were used to estimate the apportionment of gene diversity within and between populations and to construct a dendrogram based on a similarity matrix containingNei genetic distances. — The gene diversity estimates suggest that the structure ofCapsicum populations in Mexico consists of predominantly homozygous genotypes presumably due to a self-pollinated breeding system and population bottlenecks. Significant genetic differentiation was found mainly between populations of differing geographical regions.—Based on the results of this study, three species of domesticatedCapsicum can be identified in Mexico,C. annuum var.annuum, C. chinense, andC. pubescens. Semidomesticated and wild forms include two species,C. frutescens andC. annuum var.glabriusculum. A sharp geographical division results between the latter species;C. frutescens was collected exclusively in the southeastern states of Oaxaca, Chiapas, and Tabasco; whereas wild and semidomesticated forms from the rest of the country areC. annuum. Based upon the similarity of enzyme genotypes of semidomesticated and wild forms, the primary center of domestication of cultivatedC. annuum was estimated to be the region comprising the states of Tamaulipas, Nuevo Leon, San Luis Potosi, Veracruz, and Hidalgo in eastern Mexico. A possible second center of domestication is suggested to be localized in the state of Nayarit, western Mexico.     

Evaluation of genetic diversity amongst <Emphasis Type="Italic">Descurainia sophia</Emphasis> L. genotypes by inter-simple sequence repeat (ISSR) marker

Descurainia sophia is a valuable medicinal plant in family of Brassicaceae. To determine the range of diversity amongst D. sophia in Iran, 32 naturally distributed plants belonging to six natural populations of the Iranian plateau were investigated by inter-simple sequence repeat (ISSR) markers. The average percentage of polymorphism produced by 12 ISSR primers was 86 %. The PIC values for primers ranged from 0.22 to 0.40 and Rp values ranged between 6.5 and 19.9. The relative genetic diversity of the populations was not high (Gst =0.32). However, the value of gene flow revealed by the ISSR marker was high (Nm = 1.03). UPGMA clustering method based on Jaccard similarity coefficient grouped the genotypes into two major clusters. Graph results from Neighbor-Net Network generated after a 1000 bootstrap test using Jaccard coefficient, and STRUCTURE analysis confirmed the UPGMA clustering. The first three PCAs represented 57.31 % of the total variation. The high levels of genetic diversity were observed within populations, which is useful in breeding and conservation programs. ISSR is found to be an eligible marker to study genetic diversity of D. sophia.