Extensive introgression of Middle American germplasm into Chilean common bean cultivars

Summary The genetic diversity of 95. representative Chilean common bean (Phaseolus vulgaris L.) landraces was analyzed using phaseolin seed protein and eight isozyme systems as genetic markers. Four types of phaseolin were found, “C”, “T”, “S” and “H”, in decreasing order of frequency. Each type had a different distribution between the Northern and Southern regions of the country. Nei’s genetic distance based on isozyme diversity indicated that a high percentage of the total variation found in this sample occurred between landraces and only a small percentage of the variation was detected within populations. Cluster analysis based on Nei’s genetic distance and a principal component analysis of isozyme frequencies did not detect a clear association between the geographic distribution of the landraces and their isozyme constitution. However, Nei’s genetic distance analysis clustered the bean landraces into two major groups which had a specific isozyme pattern, seed color, and seed size. The genetic analysis also detected a rare polymorphism for theMdh-2 locus, a null allele at theDiap-2 locus, and polymorphism for theAco-2 locus. The principal component analysis of isozyme frequencies showed that only 30% of the genotypes analyzed were similar to the Andean check and 5% of the samples were similar to Middle American check. This finding suggests a high frequency of hybridization between the Middle America and Andean gene pools in cultivated common bean from Chile.     

Genetic erosion and in situ conservation of Lima bean (Phaseolus lunatus L.) landraces in its Mesoamerican diversity center

Lima bean (Phaseolus lunatus L.) is an important crop in traditional Mayan agriculture of the Yucatan Peninsula, Mexico, its Mesoamerican center of diversity. Genetic erosion in this species is currently a threat in this region out of 3 of 21 landraces dominate 71.24% of the cultivated area, and 12 are rare landraces grown only in 6.29%. Using 90 ISSR loci, we estimated the diversity and genetic relationships for 21 landraces to analyzing their risk of genetic erosion, and generate data for their in situ conservation. Total genetic diversity was high (h = 0.29), however it was lower than wild gene pool reported (h = 0.69). The abundant landraces had genetic diversity values lower (h = 0.13, I = 0.17) than the common (h = 0.26, I = 0.33) and rare landraces (h = 0.24, I = 0.27). However, the rare landraces are in a higher risk of genetic erosion due to local extinction. The cluster analysis showed no groups corresponding to morpho-phenological characteristics, geographic origin or traditional classification, which resulted from high inter-landraces gene flow levels. The molecular data confirmed that the domesticated Lima bean pool of the Yucatan Peninsula has a high risk of genetic erosion. If current tendencies in landrace cultivation continue, many will no longer be planted within two to three generations, with a consequent loss of their alleles. Programs urgently need to be established for in situ conservation of Lima bean landraces in this region.     

Variation in primitive landraces of common bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) from Argentina

The phenotypic variation found in four common bean (Phaseolus vulgaris L.) complex primitive landraces, among a group of accessions collected in Northwestern Argentina in several missions is described, with particular attention to the wide diversity found in some small areas. It is presented a hypothesis about the maintenance of such diversity in bean mixtures or complex primitive landraces that grow close to their wild relative. Wide diversity regarding to seed type and plant characteristics was displayed by the landraces MCM-SV (composed of 11 lines), MCM-292 (14 lines), MCM-298 (5 lines) and VAV-3716 (14 lines). Food uses of dry seed and fresh pod seemed to be more relevant than the aesthetic use although all of them were presumably considered by humans for centuries resulting in the current phenotypes of these complex primitive landraces. Additionally, some weedy types (intermediate between wild and domesticated types) were detected in the landracesMCM-292 and MCM-298. The four complex landraces described consisted of highly diverse mixtures and they could play a role in breeding to enlarge the genetic basis of domesticated bean varieties belonging to the Andean gene pool.     

Genetic Diversity and Relationships of Wheat Landraces from Oman Investigated with SSR Markers

Little is known about genetic diversity and geographic origin of wheat landraces from Oman, an ancient area of wheat cultivation. The objectives of this study were to investigate the genetic relationships and levels of diversity of six wheat landraces collected in Oman with a set of 30 evenly distributed SSR markers. The total gene diversity, (H_T), conserved in the three durum wheat (Triticum durum desf.) landraces (H_T = 0.46) was higher than in the three bread wheat (Triticum aestivum L.) landraces (H_T = 0.37), which were similar to Turkish and Mexican bread wheat landraces calculated in previous studies. Genetic variation partitioning (G_ST) showed that variation was mainly distributed within rather than among the durum (G_ST = 0.30) and bread wheat (G_ST = 0.19) landraces. Based on modified Rogers’ distance (MRD), the durum and bread wheat landraces were distinct from each other except for a few individuals according to principal coordinate analysis (PCoA). One bread wheat landrace (Greda) was separated into two distinct sub-populations. A joint cluster analysis with other landraces of worldwide origin revealed that Omani bread wheat landraces were different from other landraces. However, two landraces from Pakistan were grouped somewhat closer to Omani landraces indicating a possible, previously unknown relationship. Implications of these results for future wheat landrace collection, evaluation and conservation are discussed.     

The major Italian landraces of lentil (<Emphasis Type="Italic">Lens culinaris</Emphasis> Medik.): Their molecular diversity and possible origin

The eleven most known landraces from central and southern Italy were analysed using ISSR markers on 15 randomly chosen individuals for each landrace, with the aim of assessing genetic variation within and among landraces and possibly ascertaining their origin and genetic relationships. A total of 164 loci were observed, 128 of which (78.05%) were polymorphic. Gene diversity over all landraces was I = 0.3759. The highest within-landrace diversity was observed in samples from the Apennine ridge and for one Sicilian landrace; on the other hand, samples from the small Sicily islands were less variable. Principal Component Analysis and AMOVA allowed the discrimination of groups of landraces with higher similarity. Analyses indicate that the small Sicily islands landraces are very closely related to one another and seem to be derived from the peninsular material; moreover, they help disclose relationships among geographically close landraces. The knowledge so acquired can, therefore, contribute to elaborate strategies for increasing the economical value of élite landraces and to protect producers from frauds.     

The common bean populations from Basilicata (Southern Italy). An evaluation of their variation

The variation within a collection constituted by 36 populations of common bean (Phaseolus vulgarisL.) recently collected in Basilicata region (Southern Italy) was studied. These populations are cultivated in marginal areas of the region mainly for farms' self-consumption. An appreciable variation of seed shape, colour and type of pattern was observed; 34 populations are of climbing growth habit. The frequency of the phaseolin types within the collection was investigated. C, T and S phaseolin types were observed, the type C being predominant (18 of 36 landraces); intra-population variation was detected only for two landraces. Local populations were compared with 28 commercial cultivars widely grown in the Basilicata region and accounting for 80–90% of common bean production. Significant divergences in growth habit and frequency of phaseolin types were observed: 22 cultivars had bush growth habit and 20 showed T phaseolin type. These results stress the urgency of actions devoted to the safeguard of this local germplasm. In fact, the diffusion of alloctonous and not typical germplasm is the first step towards the erosion of useful or valuable genes present in those established local populations.     

AFLP analysis of genetic diversity in five accessions of Polish runner bean (<Emphasis Type="Italic">Phaseolus coccineus</Emphasis> L.)

Runner bean (Phaseolus coccineus L.) is traditionally cultivated in Poland for dry seeds. The national collection of runner bean maintained in the National Center for Plant Genetic Resources gathers 152 accessions, which are mainly landraces originated in Poland (68%), Ukraine (17%) and Slovakia (10%). The collection contains valuable genetic resources for bean breeders and research. The aim of this study was to describe the level and structure of genetic diversity of three landraces and two commercial cultivars of runner bean from the national collection in order to assess their genetic potential for breeding. Amplified Fragment Length Polymorphism analysis included five combinations of selective primers. Analysis of seven genetic diversity parameters reveled fair amount of genetic variation both in landraces and cultivars. High genetic diversity of commercial cultivars relative those of landraces suggests that the breeding process leading to their release was rather moderate and most likely included domestic gene pool of runner bean. Low gene diversity and low Nei’s genetic distance values as well as intergradations among accessions in the PCoA may indicate reduced variability P. coccineus grown in Poland as a result of its migration pathways.     

Genetic Diversity Among Brazilian Cultivars and Landraces of Tomato Lycopersicon Esculentum Mill. Revealed by RAPD Markers

Random amplified polymorphic DNA markers (RAPD) were used to estimate the variability of 35 tomato accessions (Lycopersicon esculentum Mill.). A total of 257 reproducibly scorable bands were obtained from 20 primers, 78.6% of which were polymorphic. The percentage distribution of RAPD markers shows a bimodal distribution, and the frequency of rare alleles is similar in commercial and landrace accessions. Genetic distances among accessions were calculated and a dendrogram showing the genetic relationships among them was constructed allowing for the separation of four groups. Twenty out of 23 Brazilian landraces fell within one group, whereas commercial cultivars were distributed in the four groups. AMOVA analysis of RAPD data showed that, despite the high within Brazilian landraces and commercial cultivars variation, these two groups are significantly different, indicating that landraces can be a source of variation for breeding programs.     

Genetic diversity in bambara groundnut (Vigna subterranea (L.) Verdc) landraces assessed by Random Amplified Polymorphic DNA (RAPD) markers

Genetic diversity in 12 landraces of bambara groundnut (Vigna subterranea), an indigenous African legume, was evaluated using Random Amplified Polymorphic DNA (RAPD) markers. DNA from individuals of each landrace was also analysed to determine the level of heterogeneity within landraces. RAPDs revealed high levels of polymorphism among landraces. The percentage polymorphism ranged from 63.2% to 88.2% with an average of 73.1% for the 16 RAPD primers evaluated. The construction of genetic relationships using cluster analysis groups the 12 landraces in two clusters. RAPDs are useful for the genetic diversity studies in V. subterranea and can identify variation within landraces.     

Characterization of Some Italian Common Bean (<Emphasis Type="Italic">Phaseolus Vulgaris</Emphasis> L.) Landraces by RAPD,Semi-random and ISSR Molecular Markers

Randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR) and a semi-random PCR system were used to analyze the genetic diversity of 16 Italian common bean landraces and their relationship to four commercial cultivars. Of the primers tested, 8 ISSR, 6 RAPD and 7 semi-random primers produced polymorphic and reproducible DNA fragments. A higher proportion of polymorphic bands were observed using ISSR (85%) and semi-random (90%) primers than RAPD (69%) method. The combination of any two semi-random markers allowed the identification of all 20 bean genotypes. In contrast ISSR (except for primer (CAC)₃GC) and RAPD markers appeared to be less informative as more than two markers were necessary to achieve the same diagnostic level. Moreover, 7 ISSR, 2 RAPD and 8 semi-random exclusive bands were identified as putative population-specific markers. Semi-random and ISSR derived dendrograms showed similar tendencies in terms of genetic relatedness, whereas clustering of genotypes within groups was not similar when compared with the RAPD technique. Despite the different ability to resolve genetic variation among the investigated landraces, two major clusters with less than 60% (ISSR) and 40% (RAPD and semi-random) genetic similarity were formed with all three marker systems. The two groups were correlated with the phaseolin patterns and seed size of the landraces. The analysis showed that the cultivar ȁ8Lingua di Fuocoȁ9 and most of the landraces (13 out of 16) collected in Italy belong to the Andean gene pool, whereas only the three populations from Pratomagno belong to the Middle American gene pool.     

Phenotypic Variation and Relationships in Landraces and Improved Varieties of Rye (Secale cereale L.) from Northern Europe

Phenotypic diversity for agronomic characteristics was determined in an experiment with 29 landraces and 14 improved varieties of rye from the Nordic area, Germany and Poland. The accessions were scored for 12 characters. Effects of the location, year, type, and country of origin for landraces were investigated with analysis of variance. Phenotypic variations for the traits were estimated using the Shannon–Weaver diversity index. The genetic variation was high, with an average of H ₀ = 0.566. The landraces from Norway, Sweden and Finland showed the highest variation, whereas the improved varieties had the lowest. The German material also had low variation but the status of this material is uncertain. The genetic diversity showed that 70% of the variation was found within the accessions. A cluster analysis was carried out to identify the relationship between the accessions. The material grouped into eight clusters, where clusters I to V included landraces from Sweden, Finland and Norway, except for cluster III, which included one improved variety from Denmark. Cluster VI comprised a single Swedish landrace from Gotland. Most of the improved varieties were in cluster VII and the last cluster contained accessions from Germany and Sweden.     

Common Bean (Phaseolus vulgaris L.) Landraces from Abruzzo and Lazio Regions (Central Italy)

Marginal areas of Central Italy, i.e., areas where socio-economic conditions are weak and agriculture is carried on with traditional farming methods, are known to retain highly interesting local legume populations. The variation within a collection constituted by 44 populations belonging to 19 common bean (Phaseolus vulgaris L.) landraces, recently collected in Central Italy, was studied. Most landraces from the Lazio region were collected in the inner valleys of Aniene river basin, those from the Abruzzo region were collected in the Valley Peligna and the basin of the Aterno–Pescara river. Some morphological traits of plant and seeds and the phaseolin pattern were analysed to evaluate the degree of genetic variation among and within the landraces. Both common bean gene pools were represented in the investigated collection, the populations belonging to Andean gene pool were predominant. The landraces ‘Cioncone’, from Lazio and ‘Fagiolo pane aquilano’, from Abruzzo showed the rare A phaseolin type. All the collected data were submitted to cluster analysis. Two main subgroups were identified, the former included mainly populations from Abruzzo region and the latter including all the others. Despite this, a considerable resemblance exists between the common bean landraces from Abruzzo and Lazio, as proved by the low rankings on the tree among the populations. The observed similarity is discussed also on the basis of historical relationships between the two sides of the Apennine ridge. Contribution n. 40 from Institute of Plant Genetics-CNR, Bari, Italy.     

Genetic evidence for speciation in <Emphasis Type="Italic">Cannabis</Emphasis> (Cannabaceae)

Sample populations of 157 Cannabis accessions of diverse geographic origin were surveyed for allozyme variation at 17 gene loci. The frequencies of 52 alleles were subjected to principal components analysis. A scatter plot revealed two major groups of accessions. The sativa gene pool includes fiber/seed landraces from Europe, Asia Minor, and Central Asia, and ruderal populations from Eastern Europe. The indica gene pool includes fiber/seed landraces from eastern Asia, narrow-leafleted drug strains from southern Asia, Africa, and Latin America, wide-leafleted drug strains from Afghanistan and Pakistan, and feral populations from India and Nepal. A third putative gene pool includes ruderal populations from Central Asia. None of the previous taxonomic concepts that were tested adequately circumscribe the sativa and indica gene pools. A polytypic concept of Cannabis is proposed, which recognizes three species, C. sativa, C. indica and C. ruderalis, and seven putative taxa.     

Genetic diversity in the Lima bean (Phaseolus lunatus L.) as revealed by chloroplast DNA (cpDNA) variations

Genetic diversity in the Lima bean (P. lunatus L.) was assessed bymeans of two chloroplast DNA probes. Based on data obtained from 152accessions including wild forms and landraces, the two separateMesoamerican and Andean groups were confirmed and a transition poolof genetic diversity was observed in the two botanical formsconsistent with their distribution range. Three primary centres ofgenetic diversity and one secondary diversification spot are proposedfor the wild Lima bean whereas only two domestication sites areunderlined for the landraces. The importance of human intervention inwidening the distribution range and the genetic diversity inlandraces is discussed.     

Genetic relationships and diversity among Brazilian cultivars and landraces of common beans (Phaseolus vulgaris L.) revealed by AFLP markers

The genetic variation and relationships among 31 accessions of Phaseolus vulgaris L., and two representatives of Vigna unguiculata L., were evaluated by AFLP analysis. A total of 263 DNA fragments across all materials were scored using nine primer combinations, averaging 32 per primer. More than 95% of the amplification products showed polymorphism, indicating high variation at the DNA level among these accessions. Pair-wise genetic similarity (Jaccard's coefficient) ranged from 0.553 to 0.840, with a mean of 0.765. Twenty-three accessions (70%) clustered into three groups. A majority of the commercial cultivars (91%) clustered within a single group, whereas the landraces were distributed along all the variation. An apparent correlation with phaseolin types was detected. Results of this study suggest that Brazilian landraces truly represent the overall genetic variability of Phaseolus vulgaris, confirming the multiple origins of these materials, and their potential as a source of variation for breeding programs.     

Performance of Common Bean (Phaseolus vulgaris L.) Landraces from Spain in the Atlantic and Mediterranean Environments

Ninety-five common bean (Phaseolus vulgaris L.) landraces from Spain were evaluated in three different environments in northern Spain for their agronomic performance and seed quality. Significant differences among landraces were found for 14 quantitative traits related to phenology, yield and its components, and seed quality traits. Environmental effects were significant for all traits evaluated except for seeds pod^?1, seed width/thickness, seed weight, and seed water absorption. Landrace by environment interactions were significant for all traits except for seeds pod^?1 and seed water absorption. Selection of new breeding lines for agronomic performance and seed quality within landraces should be reliable because many of them are mixture of lines. Some heirloom varieties belonging to the types faba, caparrón,riñón,ganxet and tolosana had the best performances regarding to seed quality and yield. Principal component analysis revealed differences among environments affecting the performance of the bean landraces. Variation in the landraces seems to be organized in a different way in each one of the test environments, therefore, low plasticity and specific adaptation of Spanish bean landraces to different environments is derived from this study. Some landraces, especially those large and white seeded should be an useful resource for sustainable farming systems in different biogeographical areas and a worthy germplasm for the genetic improvement of agronomic value and seed quality.     

Geographic variation in tetraploid wheat (Triticum turgidum spp. turgidum convar. durum) landraces from two provinces in Ethiopia

There is considerable wealth of genetical and morphological variation in tetraploid wheat collected from Ethiopia by past expeditions. Several authors have speculated on the reasons for this concentration of diversity so far removed from the centre of origin of wheats in West Asia. The present study reports results of evaluation carried out on material collected in the early 1970's from Ethiopia. The landraces from the two provinces Shewa and Tigray were found to be distinctly different. This divergence was attributed to the differences in environmental conditions between them. Wide differentiation among landraces within each province was also present. The Ethiopian farmer's practice of growing composite cultivars in the field has resulted in bulk samples of Ethiopian landraces containing several agrotypes. The proportion of total variance due to differences among agrotypes within landraces was by far the greatest found in this study, followed in most cases by the variation among landrace populations within provinces which exceeded, in turn, the variation between province gene pools. The optimal strategy for further germplasm collections and implications for improvement and conservation in locally-based community gene banks are discussed.     

Genetic structure of Lima bean (<Emphasis Type="Italic">Phaseolus lunatus</Emphasis> L.) landraces grown in the Mayan area

Lima bean (Phaseolus lunatus L.) is an important crop in the Mayan culture. The Mayan area, considered as a main center of Mesoamerican diversity, has been divided into two subareas: the Mayan lowlands and the Mayan highlands. The Yucatan Peninsula is part of the Mayan lowlands and holds the highest number of Lima bean landraces of Mexico, but Lima beans are in high risk of genetic erosion due to intensification of the traditional Mayan agriculture. However, information on genetic diversity of Lima beans of the Mayan highlands is lacking. By using 46 landraces collected in the Mayan area (23 from each subarea) and 73 ISSR loci (inter-simple sequence repeats), we analyzed the structure, diversity and genetic relationships of Lima beans of this part of Mesoamerica. High levels of diversity (H _BAY = 0.45) and genetic structure (F _ST = 0.66) were found for the whole Mayan area. Genetic diversity in the Mayan lowlands was apparently higher than the Mayan highlands (H _BAY = 0.44 and 0.36, respectively); but differences were not statistically significant. Genetic structure between the subareas was high (AMOVA = 30% of total variation), most landraces grouping according to their geographic origin. This study shows the importance of the Mayan culture in the diversification and conservation of Lima beans. The results provide important information that should be considered when implementing strategies to collect Lima bean landraces and planning in situ and ex situ programs to conserve these landraces in the Mayan region.     

Genetic relationships among cultivated and wild <Emphasis Type="Italic">Vigna angularis</Emphasis> (Willd.) Ohwi et Ohashi and relatives from Korea based on AFLP markers

Genetic variation and relationships among members of the azuki bean complex (Vigna angularis) including wild (V. angularis var. nipponensis), weedy, and cultivated types (V. angularis var. angularis), V. nakashimae, and rice bean (V. umbellata) from Korea were examined using the Amplified fragment length polymorphism (AFLP) method. AFLP analysis of 50 accessions revealed 333 (72.1%) polymorphic fragments out of 462 fragments amplified using seven primer combinations. The number of polymorphic fragments within each species was 70 in the azuki bean complex and 41 in V. nakashimae, but there was no polymorphism in rice bean. The number of shared fragments among species ranges from 142 between the azuki bean complex and V. nakashimae to 166 between the azuki bean complex and rice bean. Within the azuki bean complex, the range of shared bands was from 231 between cultivated and weedy types to 238 between cultivated and wild types. A dendrogram generated from Jaccard’s similarity matrix was divided into three groups, which correspond to V. nakashimae, azuki bean complex, and rice bean. The relationship between azuki bean and rice bean is closer than between azuki bean and V. nakashimae. Phenetic distances averaged 0.502 between the azuki bean complex and V. nakashimae and 0.467 between the azuki bean complex and rice bean. Within the azuki bean complex, the weedy type was more closely related to wild than cultivated types. But UPGMA dendrogram of the azuki bean complex reveals that each type is not clearly isolated. These results will help to understand genetic diversity and evolutionary dynamics of Vigna in Korea.