Origins of domestication and polyploidy in oca (Oxalis tuberosa; Oxalidaceae). 3. AFLP data of oca and four wild, tuber-bearing taxa

Many crops are polyploids, and it can be challenging to untangle the often complicated history of their origins of domestication and origins of polyploidy. To complement other studies of the origins of polyploidy of the octoploid tuber crop oca (Oxalis tuberosa) that used DNA sequence data and phylogenetic methods, we here compared AFLP data for oca with four wild, tuber-bearing Oxalis taxa found in different regions of the central Andes. Results confirmed the divergence of two use-categories of cultivated oca that indigenous farmers use for different purposes, suggesting the possibility that they might have had separate origins of domestication. Despite previous results with nuclear-encoded, chloroplast-expressed glutamine synthetase suggesting that O. picchensis might be a progenitor of oca, AFLP data of this species, as well as different populations of wild, tuber-bearing Oxalis found in Lima Department, Peru, were relatively divergent from O. tuberosa. Results from all analytical methods suggested that the unnamed wild, tuber-bearing Oxalis found in Bolivia and O. chicligastensis in NW Argentina are the best candidates as the genome donors for polyploid O. tuberosa, but the results were somewhat equivocal about which of these two taxa is the more strongly supported as oca's progenitor.     

AFLP data and the origins of domesticated crops.

Amplified fragment length polymorphism (AFLP) datasets have been used to construct neighbor-joining trees from which monophyletic origins for crops such as einkorn wheat, barley, and emmer wheat have been inferred. We simulated several different multiple domestication scenarios for an imaginary cereal crop and examined the resulting domesticated populations. The simulations showed that the population biology aspects of the domestication process can result in independently domesticated populations merging in such a way that a monophyletic origin is erroneously inferred when the resulting population is examined by AFLP genotyping a nd neighbor-joining analysis. The resultsbring into question the use of this method to infer the origins of real crops.     

A reconsideration of the domestication geography of tetraploid wheats

The domestication of tetraploid wheats started from their wild progenitor Triticum dicoccoides. In this paper, the geographical distribution of this progenitor is revised to include more sampling locations. The paper is based on a collection of wild and domesticated lines (226 accessions in total) analyzed by AFLP at 169 polymorphic loci. The collection includes the 69 wild lines considered by Mori et al. (2003) in their study on chloroplast DNA haplotypes of T. dicoccoides. The goal of the experiment was to reconsider which location thought to have generated the domesticated germplasm has the highest chance of being the actual site from which wild progenitors were sampled during domestication. Phylogenetic analysis of the nuclear AFLP databases indicates that two different genetic taxa of T. dicoccoides exist, the western one, colonizing Israel, Syria, Lebanon and Jordan, and the central-eastern one, which has been frequently sampled in Turkey and rarely in Iran and Iraq. It is the central-eastern race that played the role of the progenitor of the domesticated germplasm. This is supported by the cumulative results of the AFLP data from the collections of Ozkan et al. (2002) and of Mori et al. (2003), which indicate that the Turkish Karacadag population, intermixed with some Iraq-Iran lines, has a tree topology consistent with that of the progenitor of domesticated genotypes. The Turkish Kartal population belongs genetically to the central-eastern T. dicoccoides race but at the nuclear DNA level is less related to the domesticated gene pool. A general agreement between published work on tetraploid wheat domestication emerges from these results. A disagreement is nevertheless evident at the local geographical scale; the chloroplast DNA data indicate the Kartal mountains while AFLP fingerprinting points to the Karacadag Range as the putative site of tetraploid wheat domestication.     

Automated Masking of AFLP Markers Improves Reliability of Phylogenetic Analyses

The amplified fragment length polymorphisms (AFLP) method has become an attractive tool in phylogenetics due to the ease with which large numbers of characters can be generated. In contrast to sequence-based phylogenetic approaches, AFLP data consist of anonymous multilocus markers. However, potential artificial amplifications or amplification failures of fragments contained in the AFLP data set will reduce AFLP reliability especially in phylogenetic inferences. In the present study, we introduce a new automated scoring approach, called “AMARE” (AFLP MAtrix REduction). The approach is based on replicates and makes marker selection dependent on marker reproducibility to control for scoring errors. To demonstrate the effectiveness of our approach we record error rate estimations, resolution scores, PCoA and stemminess calculations. As in general the true tree (i.e. the species phylogeny) is not known, we tested AMARE with empirical, already published AFLP data sets, and compared tree topologies of different AMARE generated character matrices to existing phylogenetic trees and/or other independent sources such as morphological and geographical data. It turns out that the selection of masked character matrices with highest resolution scores gave similar or even better phylogenetic results than the original AFLP data sets.     

Stability and inheritance of methylation states at PstI sites in Pisum

The nuclear genome of pea is heavily methylated and the stability of this methylation pattern is unknown. In this study we investigated the stability of DNA methylation and its contribution to restriction fragment polymorphism as judged by AFLP fragment differences. To do this the results of a conventional AFLP analysis were compared with those obtained by a related procedure performed on pre-amplified DNA which provided a 5-methylcytosine-free DNA template (SDAFLP). Genetic mapping in a recombinant inbred (RI) population showed that polymorphisms attributable to different methylation states of PstI sites were abundant, and generally appeared to be stably inherited, although occasional failures of the inheritance of methylation states have been found. Assessments of genetic diversity by AFLP and SDAFLP were in general agreement with each other and with the currently accepted phylogeny of Pisum, but within cultivated groups the number of differences appeared to be exaggerated by AFLP. The data suggest that epigenetic differences may have played a role in the domestication of pea.     

Phylogenetic signal in AFLP data sets

AFLP markers provide a potential source of phylogenetic information for molecular systematic studies. However, there are properties of restriction fragment data that limit phylogenetic interpretation of AFLPs. These are (a) possible nonindependence of fragments, (b) problems of homology assignment of fragments, (c) asymmetry in the probability of losing and gaining fragments, and (d) problems in distinguishing heterozygote from homozygote bands. In the present study, AFLP data sets of Lactuca s.l. were examined for the presence of phylogenetic signal. An indication of this signal was provided by carrying out tree length distribution skewness (g1) tests, permutation tail probability (PTP) tests, and relative apparent synapomorphy analysis (RASA). A measure of the support for internal branches in the optimal parsimony tree (MPT) was made using bootstrap, jackknife, and decay analysis. Finally, the extent of congruence in MPTs for AFLP and internal transcribed spacer (ITS)-1 data sets for the same taxa was made using the partition homogeneity test (PHT) and the Templeton test. These analytical studies suggested the presence of phylogenetic signal in the AFLP data sets, although some incongruence was found between AFLP and ITS MPTs. An extensive literature survey undertaken indicated that authors report a general congruence of AFLP and ITS tree topologies across a wide range of taxonomic groups, suggesting that the present results and conclusions have a general bearing. In these earlier studies and those for Lactuca s.l., AFLP markers have been found to be informative at somewhat lower taxonomic levels than ITS sequences. Tentative estimates are suggested for the levels of ITS sequence divergence over which AFLP profiles are likely to be phylogenetically informative.     

Genetic comparison of Bacillus anthracis and its close relatives using amplified fragment length polymorphism and polymerase chain reaction analysis

Amplified fragment length polymorphism (AFLP) analysis allows a rapid, relatively simple analysis of a large portion of a microbial genome, providing information about the species and its phylogenetic relationship to other microbes (Vos et al. 1995). The method simply surveys the genome for length and sequence polymorphisms. The AFLP pattern identified can be used for comparison to the genomes of other species. Unlike other methods, it does not rely on analysis of a single genetic locus that may bias the interpretation of results and does not require any prior knowledge of the targeted organism. Moreover, a standard set of reagents can be applied to any species without using species-specific information or molecular probes. We are using AFLP analysis to rapidly identify different bacterial species. A comparison of AFLP profiles generated from a large battery of Bacillus anthracis strains shows very little variability among different isolates (Keim et al. 1997). By contrast, there is a significant difference between AFLP profiles generated for any B. anthracis strain and even the most closely related Bacillus species. Sufficient variability is apparent among all known microbial species to allow phylogenetic analysis based on large numbers of genetically unlinked loci. These striking differences among AFLP profiles allow unambiguous identification of previously identified species and phylogenetic placement of newly characterized isolates relative to known species based on a large number of independent genetic loci. Data generated thus far show that the method provides phylogenetic analyses that are consistent with other widely accepted phylogenetic methods. However, AFLP analysis provides a more detailed analysis of the targets and samples a much larger portion of the genome. Consequently, it provides an inexpensive, rapid means of characterizing microbial isolates to further differentiate among strains and closely related microbial species. Such information cannot be rapidly generated by other means. AFLP sample analysis quickly generates a very large amount of molecular information about microbial genomes. However, this information cannot be analysed rapidly using manual methods. We are developing a large archive of electronic AFLP signatures that is being used to identify isolates collected from medical, veterinary, forensic and environmental samples. We are also developing the computational packages necessary to rapidly and unambiguously analyse the AFLP profiles and conduct a phylogenetic comparison of these data relative to information already in our database. We will use this archive and the associated algorithms to determine the species identity of previously uncharacterized isolates and place them phylogenetically relative to other microbes based on their AFLP signatures. This study provides significant new information about microbes with environmental, veterinary and medical significance. This information can be used in further studies to understand the relationships among these species and the factors that distinguish them from one another. It should also allow the identification of unique factors that contribute to important microbial traits, including pathogenicity and virulence. We are also using AFLP data to identify, isolate and sequence DNA fragments that are unique to particular microbial species and strains. The fragment patterns and sequence information provide insights into the complexity and organization of bacterial genomes relative to one another. They also provide the information necessary for the development of species-specific polymerase chain reaction primers that can be used to interrogate complex samples for the presence of B. anthracis, other microbial pathogens or their remnants.     

Tagging the signatures of domestication in common bean (Phaseolus vulgaris) by means of pooled DNA samples

BACKGROUND AND AIMS: The main aim of this study was to use an amplified fragment length polymorphism (AFLP)-based, large-scale screening of the whole genome of Phaseolus vulgaris to determine the effects of selection on the structure of the genetic diversity in wild and domesticated populations. METHODS: Using pooled DNA samples, seven each of wild and domesticated populations of P. vulgaris were studied using 2506 AFLP markers (on average, one every 250 kb). About 10 % of the markers were also analysed on individual genotypes and were used to infer allelic frequencies empirically from bulk data. In both data sets, tests were made to determine the departure from neutral expectation for each marker using an F(ST)-based method. KEY RESULTS: The most important outcome is that a large fraction of the genome of the common bean (16 %; P < 0.01) appears to have been subjected to effects of selection during domestication. Markers obtained in individual genotypes were also mapped and classified according to their proximities to known genes and quantitative trait loci (QTLs) of the domestication syndrome. Most of the markers that were found to be potentially under the effects of selection were located in the proximity of previously mapped genes and QTLs related to the domestication syndrome. CONCLUSIONS: Overall, the results indicate that in P. vulgaris a large portion of the genome appears to have been subjected to the effects of selection, probably because of linkage to the loci selected during domestication. As most of the markers that are under the effects of selection are linked to known loci related to the domestication syndrome, it is concluded that population genomics approaches are very efficient in detecting QTLs. A method based on bulk DNA samples is presented that is effective in pre-screening for a large number of markers to determine selection signatures.     

Phylogeny of ten species of the genus Hordeum L. as revealed by AFLP markers and seed storage protein electrophoresis

The phylogenetic relationships of 60 accessions representing ten species of the genus Hordeum were investigated based on AFLP markers and seed storage protein SDS-PAGE electrophoresis. A total of 339 AFLP polymorphic markers were scored as a result of fingerprinting the studied taxa using seven AFLP primer combinations, whereas 46 polymorphic protein bands resulted from the water soluble and water non-soluble seed storage protein electrophoresis. The phylogenetic tree deduced from AFLP analysis is concordant in a large extent with that deduced from seed storage protein electrophoresis. The studied taxa were clustered according to their genome type into two main groups representing the Old and New World’s species. Inside each group the species were clustered according to their genome type. Highly significant cophenetic correlation coefficient was obtained between both AFLP (0.96) and seed storage protein (0.89) indicating the reliability of the results.     

AFLP analysis of genetic variation within the two economically important Anatolian grapevine (Vitis vinifera L.) varietal groups.

The Anatolian region of modern-day Turkey is believed to have played an important role in the history of grapevine (Vitis vinifera L.) domestication and spread. Despite this, the rich grape germplasm of this region is virtually uncharacterized genetically. In this study, the amplified fragment length polymorphisms (AFLP)-based genetic relations of the grapevine accessions belonging to the 2 economically important Anatolian table grape varietal groups known as V. vinifera 'Misket' (Muscat) and V. vinifera 'Parmak' were studied. Thirteen AFLP primer combinations used in the analyses revealed a total of 1495 (35.5% polymorphic) and 1567 (34.6% polymorphic) DNA fragments for the 'Misket' and 'Parmak' varietal groups, respectively. The unweighted pair-group method with arthimetic averaging (UPGMA) cluster analysis and principal coordinate analysis (PCA) conducted on polymorphic AFLP markers showed that both varietal groups contain a number of synonymous (similar genotypes known by different names) as well as homony mous (genetically different genotypes known by the same name) accessions. Our results also showed that 6 of the Anatolian 'Misket' genotypes were genetically very similar to V. vinifera 'Muscat of Alexandria', implying that these genotypes might have played some role in the formation of this universally known grape cultivar. Finally, the close genetic similarities found here between 'Muscat of Alexandria' and V. vinifera 'Muscat of Hamburg' support the recent suggestion that 'Muscat of Hamburg' probably originated from 'Muscat of Alexandria' through spontaneous hybridizations. Overall, the results of this study have implications for not only preservation and use of the Anatolian grape germplasm, but also better understanding of the historical role that this region has played during the domestication of grapes.     

Optimizing automated AFLP scoring parameters to improve phylogenetic resolution

The amplified fragment length polymorphism (AFLP) technique is an increasingly popular component of the phylogenetic toolbox, particularly for plant species. Technological advances in capillary electrophoresis now allow very precise estimates of DNA fragment mobility and amplitude, and current AFLP software allows greater control of data scoring and the production of the binary character matrix. However, for AFLP to become a useful modern tool for large data sets, improvements to automated scoring are required. We design a procedure that can be used to optimize AFLP scoring parameters to improve phylogenetic resolution and demonstrate it for two AFLP scoring programs (GeneMapper and GeneMarker). In general, we found that there was a trade-off between getting more characters of lower quality and fewer characters of high quality. Conservative settings that gave the least error did not give the best phylogenetic resolution, as too many useful characters were discarded. For example, in GeneMapper, we found that bin width was a crucial parameter, and that although reducing bin width from 1.0 to 0.5 base pairs increased the error rate, it nevertheless improved resolution due to the increased number of informative characters. For our 30-taxon data sets, moving from default to optimized parameter settings gave between 3 and 11 extra internal edges with >50% bootstrap support, in the best case increasing the number of resolved edges from 14 to 25 out of a possible 27. Nevertheless, improvements to current AFLP software packages are needed to (1) make use of replicate profiles to calibrate the data and perform error calculations and (2) perform tests to optimize scoring parameters in a rigorous and automated way. This is true not only when AFLP data are used for phylogenetics, but also for other applications, including linkage mapping and population genetics.     

Patterns of AFLP variation in a core subset of cultivated hexaploid oat germplasm

Many core collections have been developed from large collections of crop germplasm, but most of these have not been characterized, particularly using molecular techniques, for germplasm management and utilization. We have attempted to characterize a structured sample representing a world collection of 11,622 cultivated hexaploid oat accessions in the hope of understanding the genetic structure of the world collection. The amplified fragment length polymorphism (AFLP) technique was applied to screen 670 accessions representing 79 countries and one group of uncertain origin. For each accession, 170 AFLP polymorphic bands detected by five AFLP primer pairs were scored. Analyses of the AFLP data showed the effectiveness of the stratified sampling applied in capturing country-wise AFLP variation. The frequencies of polymorphic bands ranged from 0.11 to 0.99, with an average of 0.72. The majority (89.9%) of the AFLP variation resided within accessions of each country, and only 6.2% of the AFLP differences existed among accessions of major geographic regions. Accessions from the Mediterranean region were the most distinct, while those from Russia and the USA were the most diverse. The two distinct groups that were observed were separated largely on the basis of common oat and red oat. Red oat was genetically more diverse than its common and hull-less counterparts, and hull-less oat was more related to common oat than red oat. Landrace and non-landrace accessions displayed similar AFLP variation patterns. These patterns are significant for understanding the domestication of cultivated oat and are useful in classifying the intraspecific diversity of oat germplasm, developing specific core subsets of the oat collection, and exploring new sources of genes for oat improvement.     

Genetic variation in an endemic salamander, Salamandra atra, using amplified fragment length polymorphism

The pattern of genetic differentiation of the endemic alpine salamander, Salamandra atra, has been studied using amplified fragment length polymorphism (AFLP) from 11 populations throughout the range of the two currently recognized subspecies, atra and aurorae. Five different primer combinations produced 706 bands and were analyzed by constructing a phylogenetic tree using NJ and principal component analysis. Significant genetic variation was revealed by AFLP between and within populations but, our results show a lack of genetic structure. AFLP markers seems to be unsuitable to investigate complex and recent diversification.     

Phylogeographic relationships among Asian eggplants and new perspectives on eggplant domestication

The domestication history of eggplant (Solanum melongena L.) has long been debated, with studies unable to narrow down where domestication occurred within a broad region of tropical Asia. The most commonly hypothesized region is India, however China has an equally old written record of eggplant use dating ca. 2000 years before present. Both regions have a high diversity of landraces and populations of putatively wild eggplant: Solanum incanum L. in India and Solanum undatum Lam. in SE Asia. An additional complication is that there is taxonomic confusion regarding the two candidate progenitors. Here, we synthesize historic, morphologic, and molecular data (nrITS sequence and AFLP) to interpret the phylogeographic relationships among candidate progenitors and Asian eggplant landraces in order to test theories of domestication. A minimum of two domestication events is supported: one in India and one in southern China/SE Asia. Results also support separate domestication of S. melongena subsp. ovigerum, a group of morphologically distinct eggplants found in SE Asia, and suggest Asian S. incanum and S. undatum may not be genetically distinct. Routes of the spread of eggplant cultivation throughout Asia are proposed, and evolutionary relationships among allied species are discussed.     

Comparative analysis of phylogenetic relationships of grain amaranths and their wild relatives (Amaranthus; Amaranthaceae) using internal transcribed spacer, amplified fragment length polymorphism, and double-primer fluorescent intersimple sequence repeat markers.

The most economically important group of species in the genus Amaranthus is the A. hybridus species complex, including three cultivated grain amaranths, A. cruentus, A. caudatus, and A. hypochondriacus, and their putative wild progenitors, A. hybridus, A. quitensis, and A. powellii. Taxonomic confusion exists among these closely related taxa. Internal transcribed spacer (ITS) of nuclear ribosomal DNA, amplified fragment length polymorphism (AFLP), and double-primer fluorescent intersimple sequence repeat (ISSR) were employed to reexamine the taxonomic status and phylogenetic relationships of grain amaranths and their wild relatives. Low ITS divergence in these taxa resulted in poorly resolved phylogeny. However, extensive polymorphisms exist at AFLP and ISSR loci both within and among species. In phylogenetic trees based on either AFLP or ISSR or the combined data sets, nearly all intraspecific accessions can be placed in their corresponding species clades, indicating that these taxa are well-separated species. The AFLP trees share many features in common with the ISSR trees, both showing a close relationship between A. caudatus and A. quitensis, placing A. hybridus in the same clade as all grain amaranths, and indicating that A. powellii is the most divergent taxon in the A. hybridus species complex. This study has demonstrated that both AFLP and double-primer fluorescent ISSR have a great potential for generating a large number of informative characters for phylogenetic analysis of closely related species, especially when ITS diversity is insufficient.     

Genetic structure of Eurasian and North American Leymus (Triticeae) wildryes assessed by chloroplast DNA sequences and AFLP profiles

Leymus is a genomically defined allopolyploid of genus Triticeae with two distinct subgenomes. Chloroplast DNA sequences of Eurasian and North American species are distinct and polyphyletic. However, phylogenies derived from chloroplast and nuclear DNA sequences are confounded by polyploidy and lack of polymorphism among many taxa. The AFLP technique can resolve phylogenetic relationships between closely related species, with a curvilinear relationship expected between the proportion of shared bands and nucleotide substitution rate (D), up to about 0.100 D. The objective of this study was to compare D and phylogenetic relationships among 16 Leymus taxa, based on chloroplast DNA sequences and multi-locus AFLP genotypes. Estimates of chloroplast D between taxa were 0.002 and 0.013 within and among continental regions, respectively. Estimates of AFLP D between taxa were 0.076 and 0.093 compared within and between continental regions, respectively, versus 0.024 within taxa. Bayesian and neighbor-joining cluster analyses effectively separated all AFLP genotypes by species, but showed that North American L. ambiguus is a hybrid species with nearly equal contributions from sympatric L. cinereus and L. salinus taxa. Two hierarchical AFLP clades, containing six North American taxa and four Eurasian taxa, had more than 98% bootstrap confidence with 0.071 and 0.055 D among taxa. Three other Eurasian taxa clustered with 79% and 89% confidence, with up to 0.79 D between taxa. These estimates provide benchmarks for phylogenetic comparisons of AFLP profiles, but three taxa could not be reliably grouped, which may reflect concurrent radiation of multiple lineages or lack of homologous AFLP characters caused by a high D.     

Nuclear markers reveal that inter-lake cichlids' similar morphologies do not reflect similar genealogy

The apparent inter-lake morphological similarity among East African Great Lakes' cichlid species/genera has left evolutionary biologists asking whether such similarity is due to sharing of common ancestor or mere convergent evolution. In order to answer such question, we first used Geometric Morphometrics, GM, to quantify morphological similarity and then subsequently used Amplified Fragment Length Polymorphism, AFLP, to determine if similar morphologies imply shared ancestry or convergent evolution. GM revealed that not all presumed morphological similar pairs were indeed similar, and the dendrogram generated from AFLP data indicated distinct clusters corresponding to each lake and not inter-lake morphological similar pairs. Such results imply that the morphological similarity is due to convergent evolution and not shared ancestry. The congruency of GM and AFLP generated dendrograms imply that GM is capable of picking up phylogenetic signal, and thus GM can be potential tool in phylogenetic systematics.     

Development of molecular markers and preliminary investigation of the population structure and mating system in one lineage of black morel (Morchella elata) in the Pacific Northwestern USA

Phylogenetic analysis of LSU/ITS sequence data revealed two distinct lineages among 44 morphologically similar fruiting bodies of natural black morels (Morchella elata group) sampled at three non-burn locations in the St Joe and Kanisku National Forests in northern Idaho. Most of the sampled isolates (n = 34) represented a dominant LSU/ITS haplotype present at all three sites and identical to the Mel-12 phylogenetic lineage (GU551425) identified in a previous study. Variation at 1-3 nucleotide sites was detected among a small number of isolates (n = 6) within this well supported clade (94%). Four isolates sampled from a single location were in a well supported clade (97%) distinct from the dominant haplotypes and may represent a previously un-sampled, cryptic phylogenetic species. Species-specific SNP and SCAR markers were developed for Mel-12 lineage isolates by cloning and sequencing AFLP amplicons, and segregation of AFLP markers were studied from single ascospore isolates from individual fruiting bodies. Based on the segregation of AFLP markers within single fruiting bodies, split decomposition analyses of two SCAR markers, and population genetic analyses of SNP, SCAR, and AFLP markers, it appears that members of the Morchella sp. Mel-12 phylogenetic lineage are heterothallic and outcross in nature similar to yellow morels. This is the first set of locus-specific molecular markers that has been developed for any Morchella species, to our knowledge. These markers will prove to be valuable tools to study mating system, gene flow and genetic structure of black morels at various spatial scales with field-collected fruiting bodies and eliminate the need to culture samples in vitro.     

Locus-specific view of flax domestication history

Crop domestication has been inferred genetically from neutral markers and increasingly from specific domestication-associated loci. However, some crops are utilized for multiple purposes that may or may not be reflected in a single domestication-associated locus. One such example is cultivated flax (Linum usitatissimum L.), the earliest oil and fiber crop, for which domestication history remains poorly understood. Oil composition of cultivated flax and pale flax (L. bienne Mill.) indicates that the sad2 locus is a candidate domestication locus associated with increased unsaturated fatty acid production in cultivated flax. A phylogenetic analysis of the sad2 locus in 43 pale and 70 cultivated flax accessions established a complex domestication history for flax that has not been observed previously. The analysis supports an early, independent domestication of a primitive flax lineage, in which the loss of seed dispersal through capsular indehiscence was not established, but increased oil content was likely occurred. A subsequent flax domestication process occurred that probably involved multiple domestications and includes lineages that contain oil, fiber, and winter varieties. In agreement with previous studies, oil rather than fiber varieties occupy basal phylogenetic positions. The data support multiple paths of flax domestication for oil-associated traits before selection of the other domestication-associated traits of seed dispersal loss and fiber production. The sad2 locus is less revealing about the origin of winter tolerance. In this case, a single domestication-associated locus is informative about the history of domesticated forms with the associated trait while partially informative on forms less associated with the trait.     

魔芋种质资源的AFLP分析

利用AFLP技术对13份魔芋种质资源进行了DNA多态性分析。从10对引物中筛选出2对引物扩增基因组DNA,共获得112条带,其中64条为多态性标记,每个引物平均提供56个标记信息。UPMGA法聚类分析结果表明:魔芋资源的遗传多态性比较丰富,西盟魔芋和珠芽魔芋的关系比较近,白魔芋和花魔芋的关系比较近。