Morphological Diversity of Bambara Groundnut [Vigna subterranea (L.) Verdc.] Landraces in Tanzania

A field experiment was conducted in Tanzania for two seasons to assess the genetic diversity of bambara groundnut landraces based on morphological characters. One hundred accessions collected from a wide range of agricultural zones in the country were evaluated in a 10 × 10 triple lattice block design at Maruku station in Bukoba, Tanzania. For the qualitative characters evaluated, considerable morphological variations were observed for growth habit, pod shape and pod colour. Quantitative morphological characters such as peduncle length, number of leaves per plant, terminal leaflet width, terminal leaflet length, petiole length, plant spread, plant length, pod width, seed length, seed width, number of pods per plant, shelling percentage and days to 50% flowering showed significant variation among accessions for the two test seasons. Multivariate analysis for 15 quantitative morphological traits that showed significant variation indicated that the first four PCs with eigenvalues ≥1 accounted for 63.0 and 65.0% of the total variance among the accessions during the two test seasons, respectively. The most important loadings for PC1 and PC2 for the two seasons were terminal leaflet width, terminal leaflet length, petiole length, plant spread, plant height and pod length, pod width, seed length, seed width, numbers of pods per plant. Cluster analysis grouped bambara groundnut accessions into three major groups with respect to their geographic origins. Based on this present study, bambara groundnut landraces from Tanzania displayed a considerable diversity for morphological and agronomic traits useful for germplasm management and utilization into crop improvement.     

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.     

Agromorphological diversity of local Bambara groundnut (<Emphasis Type="Italic">Vigna subterranea</Emphasis> (L.) Verdc.) collected in Benin

Bambara groundnut (Vigna subterranea (L.) Verdc.) is a neglected and less exploited species in Benin. However, the rational use of the different landraces available involves an appropriate knowledge of their characteristics. This study examined the characteristics of 52 local landraces of Bambara groundnut traditionally cultivated in Benin based on 12 qualitative and 11 quantitative variables, in order to expose those of good qualities. After a classification based on the morphological variables of the seeds, the experimental field was installed in a completely randomized device of blocks repeated three times. The collected data was analyzed with Statistica 7.1 and NTSYS PC 2.2. softwares using qualitative characteristics (Growth’s type, Stem’s hairiness, Flower’s colour, Leave’s shape etc.). As result, the number of morphotypes increased from 18 (out of classification) to 47. Therefore, it appears that the Benin collection of Bambara groundnut is broad in morphological variability. The analysis of the principal component of the quantitative variables revealed three specific classes within the collection. The most efficient variety which belonged to the second class, had a high field yield per hectare (> 1 t/ha). The Souhouloumankpa variety yielded the earliest (103 days after sowing) in addition to the high field yield. The study also showed a positive relationship between 100 seed’s weight, their length, the number of seeds per plant and the seed’s field yield in kg/ha. For a sustainable preservation and an improvement of the available resources, a molecular characterization of the Bambara groundnut landraces in Benin Republic needs to be done.     

Selection criteria for grain yield and stability in bambara groundnut (Vigna subterranean (L) Verdc) landraces

The potential of bambara groundnut as a crop-based approach for the sustainable reduction of protein–energy malnutrition prevalent in Nigeria is still being explored. However, one of the limitations to sustainable production of this adapted species is low and unstable yield. Here, we employed multiple statistical analyses to determine traits that could be useful in predicting grain yield. Furthermore, additive main effect and multiplicative interaction and genotype × genotype × environment models were used to identify high yielding and stable landraces. Twenty-four bambara landraces were evaluated in two contrasting dry land growing seasons at four environments. Based on the results of correlation, path coefficient values and stepwise multiple regression analysis, it is reasonable to assume that seed growth rate would be effective as indirect selection criteria for grain yield improvement in this set of breeding materials under early and late planting environment. However, optimizing biomass growth rate, pod fill period, 100-seed weight, number of pods per plant and time to flowering may have important role in the improvement of grain yield in bambara groundnut. Due consideration should be given to 100-seed weight and time to flowering in the early dry and late planting environment. The possibility of successful cultivation of bambara groundnut in forest–savannah transition agricultural zone of Nigeria, particularly when planting is done around early August has been established in this study. However, based on the strong association between seed yield and its related characters in early and late planting environments, selection for higher seed growth rate combined with large number of pods appears to be the best indirect traits when selecting bambara groundnut plants to enhance grain yield under early and late planting environments. While landraces TVSu 1520 and 1578 were considered the best adapted landraces, TVSu 1670 and 1518 are promising landraces that could contribute to increasing grain yield stability.     

Genetic diversity analysis of yams (Dioscorea spp.) cultivated in China using ISSR and SRAP markers

Yam (Dioscorea spp.) is widely cultivated in China and many landraces are maintained by local farmers. However, there is little information available about their diversity and species identity. In this study, inter simple sequence repeat (ISSR) and sequence related amplified polymorphism (SRAP) techniques were used to assess genetic diversity within 21 yam landraces from seven cultivated populations. We observed high level of polymorphism among these landraces, specifically, 95.3 % for ISSR and 93.5 % for SRAP. Analysis of molecular variance revealed a significantly greater variation among the four yam species (40.39 %) and their populations (35.78 %) than within the populations (23.83 %). The unweighted pair group method arithmetic averages clusters and principal component analysis for 21 landraces formed four well-separated groups containing landraces of each of the four species, namely, Dioscorea opposita Thunb., Dioscorea alata L., Dioscorea persimilis Prain et Burkill, and Dioscorea fordii Prain et Burkill. The ISSR and SRAP primers were highly discriminatory among the 21 landraces; all 21 landraces could be easily differentiated using these primers. The average mean of gene flow (Nm = 0.1081) estimated from high genetic differentiation (Gst = 0.8222) suggested that gene flow among the populations was relatively restricted. The lack of genetic diversity within individual yam species suggests that it is critical to develop long-term strategies for enhancing genetic diversity within various yam species.     

Target region amplification polymorphism (TRAP) for assessing genetic diversity and marker-trait associations in chickpea (Cicer arietinum L.) germplasm

The effective utilization of crop diversity held in genebanks depends on our knowledge of useful traits and available markers associated with the target traits. Target region amplification polymorphism (TRAP) was used to evaluate the genetic diversity and underlying relationships among 263 accessions of chickpea landraces maintained by the USDA-ARS Western Regional Plant Introduction Station in Pullman, WA, USA. Two-hundred sixty-two TRAP markers were amplified by eight primer combinations. Altogether, 110 (42 %) markers were polymorphic, the other 152 (58 %) displayed no variation. These polymorphic markers revealed important differences among the accessions, with an estimated, mean pair-wise genetic distance of 25.82 %, ranging from 2.8 to 50.0 %. Genetic distance analysis divided the accessions into two major groups, with 113 and 150 accessions each, and substantial association between molecular diversity and geographic origin was evident. Bayesian analysis of population structure revealed two groups (K = 2) with evidence for six sub-groups. Additionally, the population structure of a subset of 110 lines was determined (K = 3) for testing marker-trait associations (MTAs). Phenotypic traits included the concentrations of protein and nine mineral elements in the seeds. Two MTAs were significant (p < 0.01) for concentrations of Ca and K, and three MTAs were significant for Cu and Ni concentrations. The results indicate that this population is useful for genome-wide association studies on other economic traits given the level of genetic diversity uncovered and the marker-trait associations in seed minerals discovered.     

Genetic diversity among Polish landraces of common oat (Avena sativa L.)

All over the world about 220,000 accessions of the genus Avena is preserved in gene banks. Polish oats collection, in the National Centre for Plant Genetic Resources, consists of about 2,500 accessions. More than 80 % of them belong to the species Avena sativa. Only 136 accessions have the landrace or traditional cultivar status and 91 of them were collected in Poland. The main objective of this study was to estimate genetic diversity of a set of 67 Polish landraces using inter simple sequence repeat (ISSR) markers. We also tried to determine whether genetic diversity depended on the region and altitude of collection site and if there was a relationship between DNA polymorphism and some morphological traits. The accessions were collected between years 1973 and 1999 from areas of Northern, Southern and Eastern Poland. The obtained results indicated a relatively low diversity (0.09–0.37) of the common oat landraces. Analysis of molecular variation (AMOVA) showed that there were no significant differences within designated geographic regions. It indicated that at the same time the altitude of collection site had significant effect on the genetic differentiation of the accessions. AMOVA also showed the presence of variance between groups formed on the basis of the colour of lemma. White lemma accessions were also characterized by highest genetic distinctiveness. Considering the evident impact of local climatic conditions on the genetic distinctiveness of Polish landraces utility of them in the Polish breeding programs should be considered.     

Variations in morphological and agronomic traits among Jerusalem artichoke (Helianthus tuberosus L.) accessions

Jerusalem artichoke is a diversely-utilized crop. Selection for high yield, inulin content and other economically important traits are useful for improving this crop. The objectives of the present study were to evaluate genetic variability for qualitative and quantitative traits among Jerusalem artichoke accessions and to identify different groups of accessions using morphological and agronomic traits. Seventy-nine accessions were evaluated in a randomized complete block design with two replications in the late rainy season 2008, the early rainy season 2009 and the late rainy season 2009 at Khon Kaen University agronomy farm, Thailand. Morphological and agronomic characteristics were evaluated for genetic variations. High variations were found among Jerusalem artichoke accessions for qualitative and quantitative characters, and selection for these characters is possible. High variations were observed for tuber width, number of tubers/plant, biomass, fresh tuber yield and tuber size. Correlation coefficient between fresh tuber yield and tuber size was positive and significant (0.58, P ≤ 0.01). Improvement of tuber size is a means to improve yield and tuber quality. Based on morphological and agronomic characteristics, Jerusalem artichoke accessions were clustered into four distinct groups (R² = 0.88). These groups may be used as parental material to generate progenies for further improvement of this crop. This information will enable breeders to make informed decisions about possible heterotic groups for their breeding programs and germplasm conservation.     

Genetic, morphological and cyanogen content evaluation of a new collection of Caribbean Lima bean (Phaseolus lunatus L.) landraces

Lima bean is a species cultivated broadly in the Americas and has been cultivated in the Caribbean for at least 500 years. In order to determine the genetic structure and diversity of Lima bean from the Caribbean, 50 landraces from Haiti, the Dominican Republic and Puerto Rico were collected and analyzed using 24 SSR markers. All landraces in this Caribbean collection were found to be of Middle-American descent. The genetic diversity (H_E) was highest in the landraces from Puerto Rico and lowest in Haitian landraces. The observed proportion of heterozygotes (H_O) was higher in the Haitian landraces and lowest in Puerto Rican landraces. Unweighted pair-group method with arithmetic averaging analysis showed that the landraces clustered into 3 clusters with all Haitian landraces grouping in one cluster. We also assessed the agro-morphological characteristics of the collection as well as the content of cyanogenic glucoside, linamarin, in leaves and dry seeds. Lima bean, which is a model crop for indirect plant defenses against herbivory, also possess linamarin as a source of direct plant defense. Upon tissue damage, linamarin is converted to toxic hydrogen cyanide. In our collection 44.6 % of the landraces had average seed HCN content ≤200 ppm which is the permitted level for Lima bean seed in the US. Our results also identified the landraces in this collection which have high linamarin levels in the leaves while having low levels in the seeds. Such landraces have the desirable combination of traits and will be the focus of our future plans for agronomic trait improvement though breeding.     

Water yam (Dioscorea alata L.) diversity pattern in Brazil: an analysis with SSR and morphological markers

Substantial progress was made in the last decade in understanding the diversity in Dioscorea species. However, most of the studies so far concentrated in the ‘yam belt in Africa’. We present a genetic diversity and structure analysis among commercial and local varieties of water yam (Dioscorea alata L.) in Brazil using microsatellite and morphological markers. Twelve microsatellite primers were used to generate DNA profiles of 72 local varieties and 17 commercial accessions of water yam collected in four different regions in Brazil. Also, four morphological traits were evaluated on individual plants under field conditions. The morphological characterization showed considerable diversity. High polymorphism was found with 100 % polymorphism observed for 11 primers and a discriminating power value of 0.92, on average. We did not observe a strong population structure among sampling regions, while most of the genetic diversity was concentrated within regions (95.9 %). Analysis of the relationship between accessions did not clearly separate the local and commercial genotypes. However, the molecular analyses of D. alata showed high intraspecific diversity in local accessions from different regions in Brazil, with the highest Shannon index value (H′ = 0.41) for the Southeast region. These results confirmed an admixture of accessions in all sampling regions, consistent with the lack of a significant correlation between geographic and genetic distances, suggesting that farmers exchanged water yam materials extensively. The genetic diversity can be explained by the result of a continuous exchange of accessions by farmers throughout Brazil.     

Bambara groundnut (Vigna subterranea) seed quality in response to water stress on maternal plants

Farmers who still cultivate bambara groundnut (Vigna subterranea) rely on landraces and seed retained from previous harvests. Given that the crop is typically cultivated in semi-arid regions, seed quality of farmers' retained seed might be compromised due to water stress experienced by maternal plants during production. The aim of this study was to determine the effect of water stress on maternal plants on subsequent seed quality of bambara groundnut. A single bambara groundnut landrace was characterised into four distinct selections based on seed coat and speckling colour. Initial seed quality (viability and vigour) was evaluated prior to planting seed in a field trial under irrigated and rainfed conditions. Final yield and yield components were determined at harvest. Thereafter, seed quality (viability and vigour) of progeny of different landrace selections was evaluated. Yield was lower under rainfed than irrigated conditions. Overall, subsequent seed quality showed improvement from initial seed quality of the original seedlot. Seed viability was higher in seeds produced under irrigated than rainfed conditions. Seed quality of bambara groundnut may be reduced underwater-limited production conditions. Seed enhancement practices such as priming may assist farmers to achieve better emergence. In the long term, seed production should be done under optimum conditions in order to achieve high-seed quality.     

Geographical distribution of traits and diversity in the world collection of pearl millet [<Emphasis Type="Italic">Pennisetum glaucum</Emphasis> (L.) R. Br., synonym: <Emphasis Type="Italic">Cenchrus americanus</Emphasis> (L.) Morrone] landraces conserved at the ICRISAT genebank

The genebank at ICRISAT conserves the largest collection of 23,092 pearl millet germplasm accessions originating in 52 countries. A total of 15,979 landraces originating in 34 countries and having geographic coordinates of the collection sites were selected to investigate the geographical distribution of pearl millet traits and diversity in the collection. Results revealed adaptation of pearl millet to latitudes ranging between 33.00°S and 36.91°N. Landraces with early flowering (33–40 days) were predominant in Pakistan, Ghana, Togo and India; with very late flowering (121–159 days) in Sierra Leone and the Central African Republic; with short plant height (80–100 cm) in India, Zambia and Sudan; with tallness (401–490 cm) in Chad, Burkina Faso, Nigeria and the Central African Republic; with high tillering (11–35) in India and Yemen; with high panicle exsertion (11–29 cm) in Ghana, Chad, India and Yemen; with long panicles (75–135 cm) in Nigeria and Niger; with thick panicles (41–58 mm) in Namibia, Togo and Zimbabwe and those with large seeds (16–19 g 1000 seeds^?1) were predominant in Togo, Benin, Ghana and Burkina Faso. Collections from Ghana for flowering (36–150 days), Burkina Faso for plant height (80–490), India and Yemen for total (1–35) and productive (1–19) tillers per plant, Niger for panicle exsertion (?45 to 21.0), panicle length (9–135 cm) and thickness (12–55 mm) and Zimbabwe for 1000 seed weight (3.5–19.3 g), were found as important sources for trait diversity. Launching collection missions for trait-specific germplasm is suggested to enrich the world collection of pearl millet at ICRISAT genebank for diversity.     

Morphological diversity of panicle traits in Kam fragrant glutinous rice (<Emphasis Type="Italic">Oryza sativa</Emphasis>)

Panicle traits are the most intuitive and representative features of rice germplasm resources that have been utilized in the determination of its identity, genetic diversity, yield, and quality. Based on the approaches of ethnobotany, cultural anthropology and plant morphology, we analyzed the panicle traits of 95 traditional Kam fragrant glutinous rice landraces according to folk classification in Qiandongnan Prefecture of Guizhou Province in the past 10 years. A total of 95 Kam fragrant glutinous rice landraces were tested, of which 91% consisted of those with awns, and landraces with awn lengths of 2–6 cm comprised 62%. The coefficient of variation (CV) of awn color, husk color and Grain color was more than 50%, thereby indicating extensive morphological variations among the traditional Kam fragrant glutinous rice landraces. The average Shannon–Wiener value (diversity index, H′) for panicle qualitative traits was 0.50, which was significantly higher than that of quantitative traits (0.22), thereby indicating a relatively higher degree of genetic diversity among qualitative traits. Cluster analysis of panicle morphological traits showed that 95 Kam fragrant glutinous rice landraces could be divided into five categories, using the Euclidean distance of 0.68 as threshold. Each cultivar manifested unique panicle traits. The present study on the morphological diversity of Kam fragrant glutinous rice landraces provided basic information that may be utilized for the conservation and sustainable use of Kam fragrant glutinous rice landraces.     

The Sierra Norte of Madrid: an agrobiodiversity refuge for common bean landraces

At the mountain area close to the city of Madrid, common beans were one of the main food crops present in everyday diet until 1960. This paper describes the morphological diversity, for forty-six phenological and morphological traits, found in forty-three traditional varieties of common beans collected in this area and seven commercial varieties used as reference. That comparison suggests that common bean breeding programs have led to later varieties with a higher production of straight pods. Quantitative traits showed also similar values when compared to the Iberian common bean collection, except for the phenological and seed size characters. The phenological differences could suggest an ecological adaptation of the studied landraces to the regional environmental conditions. The different seed size averages of both collections might correspond to the scarce presence of smaller seed-type common beans in Madrid collection. All the accessions collected in the Sierra Norte of Madrid belong to any of the groups included in the Spanish core collection. Madrilenian collection is also composed by indeterminate growth habit varieties, while the presence of bush accessions is relatively uncommon. Most of the Madrilenian landraces have a remarkable fitness for green-pod consumption (42 %) and their seeds are mainly white (30 %), ovate-shape (49 %) and medium-large (40 %). The study of seed storage protein allowed to classify the landraces according to their domesticated gene pools. Most of them (72 %), with T and C phaseolin type, seem to belong to Andean germplasm, while the remaining (28 %), with S and B phaseolin type, to Mesoamerican one. The remarkable morphological diversity of common beans found in this small area is a symptom of a broad genetic base despite genetic erosion, what indicates a widespread crop in the past. Therefore, it is advisable to design agro-environmental policies to promote the production and commercialization of common bean landraces in Sierra Norte of Madrid.     

Nitrogen Fixation and N-Balance Studies on Bambara Groundnut (Vigna subterranea L. Verdc) Landraces Grown on Tropical Acidic Soils of Malaysia

Bambara groundnut has great potential as an alternative crop for improving food security in its production regions and beyond. A field experiment was conducted at the Field Research Centre of the Crops for the Future to obtain information on the nitrogen (N) fixation and N balance of Bambara groundnut landraces on tropical acidic soils of Malaysia. Treatments consisted of three Bambara groundnut landraces (Ex-Sokoto, Kaaro, and NN-1) laid out in a randomized complete block design replicated three times. Results obtained revealed that Ex-Sokoto landrace was greater in yield and N fixation, whereas N balance (-haulm) was greater in NN-1 landrace. The results revealed grain yield of 703–2256 kg ha^?1 and N fixation from 32–81 kg ha^?1 and suggest that Bambara groundnut could be integrated into a cereal-based cropping system. Ex-Sokoto landrace appeared to be the most promising for yield and N fixation under Malaysian acidic soil conditions.     

Genetic diversity and population structure of a common bean (Phaseolus vulgaris L.) collection from Calabria (Italy)

Eighty-seven Phaseolus vulgaris landraces, still cultivated in Calabria (Italy), were investigated in order to study the patterns of common bean genetic diversity in this region, to better understand the evolutionary development of beans in Europe and to properly manage these genetic resources. Four American accessions and five Italian varieties were also included. Different markers, such as 12 microsatellites, seed traits, phaseolins and 100-seed weight were combined with different statistical approaches. For each microsatellite, expected (H _e ) and observed (H _o ) heterozygosities, polymorphism information content (PIC), probability of identity (PI) and homozygosity were calculated. Furthermore, in Calabrian group of bean landraces, total (N _a ) and private (N _pa ) number of alleles, observed (H _o ), expected heterozygosities (H _e ) and allelic richness (AR) were calculated. Genetic distances among landraces were estimated using Nei’s coefficient and a cluster analysis using the UPGMA algorithm was performed. The results clearly indicated that: (1) Calabrian germplasm showed a high level of diversity (H _e  = 0.595); (2) Mesoamerican and Andean gene pools were clearly distinguished in Calabrian germplasm, with the Andean gene pool predominating (83 %); (3) Calabrian landraces were largely hybridized within and between the gene pools. A model-based approach, using the STRUCTURE software, was adopted. Six groups, including 4 of Andean origin and one of Mesoamerican origin were identified. Even more interesting, a small group (8 %) showed a distinct genetic structure, in which interspecific hybridizations with runner bean (Phaseolus coccineus L.) could have occurred. Nevertheless, a relatively high proportion of Calabrian bean landraces (12.6 %) was derived from intra and interspecific hybridizations.     

Genetic diversity of anchote (Coccinia abyssinica (Lam.) Cogn.) from Ethiopia as revealed by ISSR markers

Anchote (Coccinia abyssinica) is plant endemic in Ethiopia with a high calcium content grown for its edible tuberous roots. In spite of its importance as food security crop, there is no information available on molecular genetic diversity of this crop. Therefore, the aim of this study was to assess genetic diversity within and among 12 populations of anchote using ISSR markers. Using nine ISSR primers, a total of 87 scorable bands was generated of which 74 were polymorphic. Within population diversity based on polymorphic bands ranged from 13.8 to 43.53 % with a mean of 33.05 %, Nei’s genetic diversity of 0.04–0.156 with a mean of 0.12, Shannon information index of 0.07–0.23 with a mean of 0.175 and analysis of molecular variation (AMOVA) of 51.4 % were detected. With all diversity parameters, the highest diversity was obtained from Gimbi, Bedele and Ale populations, whilst the lowest was from Manna. AMOVA showed a 48.56 % between populations variability and significantly lower than that of within population variation. Population differentiation with F_ST was 48.56 %. From Jaccard’s pairwise similarity coefficient, Decha and Nedjo were most related populations exhibiting 0.76 similarity and Manna and Nedjo were the most distantly related populations with similarity of 0.52. The only pentanucliotide primer used in the study, Primer 880 (GGAGA)3, showed a unique band in some individuals that appeared to be associated with morphological quantitative traits (lowest seed number, high protein content, largest fruit size and smallest vine length). Illubabor and Gimbi populations exhibited highest genetic diversity so that the populations should be considered as the primary sites in designing conservation areas for this crop.