Yam Diversity Research Articles

TRADITIONAL KNOWLEDGE IN CONSERVATION AND FARMING PRACTICES OF WATER YAM (DIOSCOREA ALATA L.): LESSONS LEARNED FROM EAST JAVANESE COMMUNITY

Water yam (Dioscorea alata L.) is an underutilized crop but plays a crucial role in food security of small and marginal rural families. For centuries, local farmers have planned agricultural production while conserving natural resources by adopting traditional knowledge (TK). This study aims to documents the importance of TK on water yam diversity, conservation and farming practices from the East Javanese community, a case study in Tuban Regency, Indonesia. The data collection was using a purposive sampling through interviews and direct participatory activities. Results showed that at least seven water yam local varieties were recognized with high tuber morphological variations, namely Uwi Bangkulit, Uwi Putih, Uwi Legi, Uwi Ungu, Uwi Sego, Uwi Klelet, and Uwi Randu. The variety naming mostly reflects distinct morphology and perceptual characteristics. The farmer’s reasons to cultivate variety are related to the economic value and consumable preference. Three farming systems were identified including home garden, dry land agriculture and agroforestry. The cultivation patterns are adjusted to the climatic and seasonal changes for many years, with good management practices from seed and soil preparation, planting and crop maintenance, to tuber harvest, storage and marketing. Miscellaneous uses of water yam are also documented for their sustainable livelihoods. This study can serve as a framework for decision-making at local and national level for conservation efforts and further development in cultivation management and utilization of water yam.

Optimisation and implementation of cryopreservation protocol for cassava and yam diversity long-term safeguarding

Optimisation and implementation of cryopreservation protocol for cassava and yam diversity long-term safeguarding

Starch granule size and shape characterization of yam (Dioscorea alata L.) flour using automated image analysis.

Roots, tubers and bananas (RTB) play an essential role as staple foods, particularly in Africa. Consumer acceptance for RTB products relies strongly on the functional properties of, which may be affected by the size and shape of its granules. Classically, these are characterized either using manual measurements on microscopic photographs of starch colored with iodine, or using a laser light-scattering granulometer (LLSG). While the former is tedious and only allows the analysis of a small number of granules, the latter only provides limited information on the shape of the starch granule. In this study, an open-source solution was developed allowing the automated measurement of the characteristic parameters of the size and shape of yam starch granules by applying thresholding and object identification on microscopic photographs. A random forest (RF) model was used to predict the starch granule shape class. This analysis pipeline was successfully applied to a yam diversity panel of 47 genotypes, leading to the characterization of more than 205 000 starch granules. Comparison between the classical and automated method shows a very strong correlation (R2 = 0.99) and an absence of bias for granule size. The RF model predicted shape class with an accuracy of 83%. With heritability equal to 0.85, the median projected area of the granules varied from 381 to 1115 μm2 and their observed shapes were ellipsoidal, polyhedral, round and triangular. The results obtained in this study show that the proposed open-source pipeline offers an accurate, robust and discriminating solution for medium-throughput phenotyping of yam starch granule size distribution and shape classification. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Genetic diversity and population structure of Uganda's yam (Dioscorea spp.) genetic resource based on DArTseq.

Assessing the genetic diversity of yam germplasm from different geographical origins for cultivation and breeding purposes is an essential step for crop genetic resource conservation and genetic improvement, especially where the crop faces minimal attention. This study aimed to classify the population structure, and assess the extent of genetic diversity in 207 Dioscorea rotundata genotypes sourced from three different geographical origins. A total of 4,957 (16.2%) single nucleotide polymorphism markers were used to assess genetic diversity. The SNP markers were informative, with polymorphic information content ranging from 0.238 to 0.288 and a mean of 0.260 across all the genotypes. The observed and expected heterozygosity was 0.12 and 0.23, respectively while the minor allele frequency ranged from 0.093 to 0.124 with a mean of 0.109. The principal coordinate analysis, model-based structure and discriminant analysis of principal components, and the Euclidean distance matrix method grouped 207 yam genotypes into three main clusters. Genotypes from West Africa (Ghana and Nigeria) had significant similarities with those from Uganda. Analysis of molecular variance revealed that within-population variation across three different geographical origins accounted for 93% of the observed variation. This study, therefore, showed that yam improvement in Uganda is possible, and the outcome will constitute a foundation for the genetic improvement of yams in Uganda.

Variability and genetic merits of white Guinea yam landraces in Nigeria.

Landraces represent a significant gene pool of African cultivated white Guinea yam diversity. They could, therefore, serve as a potential donor of important traits such as resilience to stresses as well as food quality attributes that may be useful in modern yam breeding. This study assessed the pattern of genetic variability, quantitative trait loci (QTLs), alleles, and genetic merits of landraces, which could be exploited in breeding for more sustainable yam production in Africa. A total of 86 white Guinea yam landraces representing the popular landraces in Nigeria alongside 16 elite clones were used for this study. The yam landraces were genotyped using 4,819 DArTseq SNP markers and profiled using key productivity and food quality traits. Genetic population structure through admixture and hierarchical clustering methods revealed the presence of three major genetic groups. Genome-wide association scan identified thirteen SNP markers associated with five key traits, suggesting that landraces constitute a source of valuable genes for productivity and food quality traits. Further dissection of their genetic merits in yam breeding using the Genomic Prediction of Cross Performance (GPCP) allowed identifying several landraces with high crossing merit for multiple traits. Thirteen landraces were identified as potential genitors to develop segregating progenies to improve multiple traits simultaneously for desired gains in yam breeding. Results of this study provide valuable insights into the patterns and the merits of local genetic diversity which can be utilized for identifying desirable genes and alleles of interest in yam breeding for Africa.

Diversity of white Guinea yam (Dioscorea rotundataPoir.) cultivars from Benin as revealed by agro-morphological traits and SNP markers

AbstractWhite Guinea yam (Dioscorea rotundataPoir.) is indigenous to West Africa, a region that harbours the crop's tremendous landrace diversity. The knowledge and understanding of local cultivars’ genetic diversity are essential for properly managing genetic resources, conservation, sustainable use and their improvement through breeding. This study aimed to dissect phenotypic and molecular diversity of white yam cultivars from Benin using agro-morphological and single nucleotide polymorphism (SNP) markers. Eighty-eight Beninese white Guinea yam cultivars collected through a countrywide ethnobotanical survey were phenotyped with 53 traits and genotyped with 9725 DArT-SNP. Multivariate analysis using phenotypic traits revealed 30 traits as most discriminative and explained up to 80.78% of cultivars’ phenotypic variation. Assessment of diversity indices such as Shannon–Wiener (H′), inverse Shannon (H.B.), Simpson's (λ) index and Pilou evenness (J) based molecular and phenotypic data depicted a moderate genetic diversity in Beninese white Guinea yam cultivars. Genetic differentiation of cultivars among country production zones was low due to the high exchange of planting materials among farmers of different regions. However, there was high genetic diversity within regions. Hierarchical clusters (HCs) on phenotypic data revealed the presence of two groups while HCs based on the SNP markers and the combined analysis identified three genetic groups. Our result provided valuable insights into the Beninese white Guinea yam diversity for its proper conservation and improvement through breeding.

Uncovering the genetic diversity of yams (Dioscorea spp.) in China by combining phenotypic trait and molecular marker analyses.

Yam is an important edible tuber and root plant worldwide; China as one of the native places of yams has many diverse local resources. The goal of this study was to clarify the genetic diversity of the commonly cultivated yam landraces and the genetic relationship between the main yam species in China. In this study, 26 phenotypic traits of 112 yam accessions from 21 provinces in China were evaluated, and 24 simple sequence repeat (SSR) and 29 sequence‐related amplified polymorphism (SRAP) markers were used for the genetic diversity analysis. Phenotypic traits revealed that Dioscorea opposita had the highest genetic diversity, followed by D. alata, D. persimilis, D. fordii, and D. esculenta. Among the 26 phenotypic traits, the Shannon diversity indexes of leaf shape, petiole color, and stem color were high, and the range in the variation of tuber‐related traits in the underground part was higher than that in the aboveground part. All accessions were divided into six groups by phenotypic trait clustering, which was also supported by principal component analysis (PCA). Molecular marker analysis showed that SSR and SRAP markers had good amplification effects and could effectively and accurately evaluate the genetic variation of yam. The unweighted pair‐group method with arithmetic means analysis based on SSR‐SRAP marker data showed that the 112 accessions were also divided into six groups, similar to the phenotypic trait results. The results of PCA and population structure analysis based on SSR‐SRAP data also produced similar results. In addition, the analysis of the origin and genetic relationship of yam indicated that the species D. opposita may have originated from China. These results demonstrate the genetic diversity and distinctness among the widely cultivated species of Chinese yam and provide a theoretical reference for the classification, breeding, germplasm innovation, utilization, and variety protection of Chinese yam resources.

Agro morphological diversity of Yams (Dioscorea spp.) Landraces from Southwest Ethiopia assessed through quantitative and qualitative traits

Yams (Dioscorea spp.) are an important crop widely cultivated for food, feed and medicine in different areas of the world. Knowledge on genetic diversity among yam landraces is essential for breeding and conservation strategies. The objective of this study was to assess the level of genetic diversity present among yam landraces using morphological traits. Thirty-six yam landraces were phenotyped at at Jimma Agricultural Research Center during 2015/16 growing season. The experiment was laid out in 6x6 simple lattice design with two replications. Data were collected on nine quantitative and ten qualitative traits, and subjected to hierarchal cluster, correlation and principal component analyses. A dendrogram was constructed using the unweighted pair group method with arithmetic mean. Tuber fresh weight showed a positive and significant association with tuber length and tuber diameter. The principal component analysis revealed five important principal components that accounted for 56.9% of the total variation observed among landraces. Principal components 1, 2, 3, 4 and 5, respectively, correlated with leaf length, leaf width and vine length A dendrogram revealed three main clusters of landraces. The most diverse landraces identified were 27/02, 21/02, 06/2000 and 68/02, which are useful for breeding and conservation. The diversity observed among the yam landraces could be useful in improvement of yams for various traits.

Assessing morphological diversity in Ethiopian yams (Dioscorea spp.) and its correspondence with folk taxonomy

This study was conducted with the objective to investigate the diversity of wild and cultivated yams based on morphological characters and to assess its correspondence with folk taxonomy. The local classification system in South-west Ethiopia was studied by recording attributes of each landrace used in the folk taxonomy. Farmers differentiate various named plants based on variations in morphological, physiological, plant cycle and tuber quality attributes. A total of 75 accessions representing 30 differently named landraces were assessed using 37 qualitative and 13 quantitative characters. Principal component analysis showed that all the traits used were useful for capturing the variability among accessions. Traits such as leaf position, twining direction, type of tuber, petiole colour on young leaves, the entire wing traits, flowering and size of leaves were useful for capturing the variability among species. All the other traits were useful for capturing the variability among accessions of the same and different species. The cluster study separated the 75 accessions into four and five major clusters based on qualitative and quantitative traits, respectively. The study indicates that the local classification corresponds well with the morphological variability, but farmers somewhat underestimate the diversity of yams at lower level taxa. Our study shows the existence of high phenotypic polymorphism among accessions, which could be exploited, if improvement need arises. Yet, regarding the validity of member species in the D. cayenensis complex, many questions remain confusing, and will need to be solved with DNA-based studies.

Indigenous biosystematics of yams (Dioscorea spp.) in Southwest Ethiopia: folk taxonomy, ethnolinguistic analysis, and folk descriptors

BackgroundIn Southwest Ethiopia, various plant species are coexisting in wild and cultivated forms. This provides an ideal setting for studying folk biosystematics of neglected species. One of such species is the Dioscorea species, in which we studied to assess the commonly applied folk wisdom of identifying, naming, and classifying yams by Sheko and Bench farmers.MethodsThis study was conducted in Bench-Maji and Sheka Zones using 272 farmers. Data on the lists of local names and system of folk taxonomy; the inherent logic, etymons, and consistency of names; and the folk descriptors and other criteria involved in taxonomy were collected. Data were collected by establishing participatory research appraisal tools, i.e., informant interviews and researcher direct observation.ResultsThe result suggests that there exists a well-developed folk taxonomic system in Sheko and Bench. This is evident in the recognition of four distinct folk ranks: sub-variety, variety, supra-variety, and folk generic. Taxa assigned to each ranks have distinct features that mark them as members of a separate categories. Farmers over-differentiate 58 individual taxa at the intraspecific levels. Of these, 37 represented varietal taxa while the rest are sub-varietal taxa. Structurally, over 78% of the varieties are labeled with unitary names while all the sub-varieties consisted of binomial names. Farmers used a total of 26 characters and 74 character states for identifying the different taxa. More than 84% of these refer to aspects of plant characteristics. Tuber characters played a key role in the local identification of varietal and sub-varietal taxa while contexts and gender played a key role in the recognition of supra-variety groups.ConclusionsThis study documented a great wealth of knowledge on indigenous biosystematics of yams, constitutes an essential step towards setting development priorities aimed at in situ conservation. The study clearly demonstrated the value of folk biosystematics for assessing the actual extent and spatial dynamics of yam diversity in traditional farming.

The Dioscorea Genus (Yam)-An Appraisal of Nutritional and Therapeutic Potentials.

The quest for a food secure and safe world has led to continuous effort toward improvements of global food and health systems. While the developed countries seem to have these systems stabilized, some parts of the world still face enormous challenges. Yam (Dioscorea species) is an orphan crop, widely distributed globally; and has contributed enormously to food security especially in sub-Saharan Africa because of its role in providing nutritional benefits and income. Additionally, yam has non-nutritional components called bioactive compounds, which offer numerous health benefits ranging from prevention to treatment of degenerative diseases. Pharmaceutical application of diosgenin and dioscorin, among other compounds isolated from yam, has shown more prospects recently. Despite the benefits embedded in yam, reports on the nutritional and therapeutic potentials of yam have been fragmented and the diversity within the genus has led to much confusion. An overview of the nutritional and health importance of yam will harness the crop to meet its potential towards combating hunger and malnutrition, while improving global health. This review makes a conscious attempt to provide an overview regarding the nutritional, bioactive compositions and therapeutic potentials of yam diversity. Insights on how to increase its utilization for a greater impact are elucidated.

Genome-wide genotyping elucidates the geographical diversification and dispersal of the polyploid and clonally propagated yam (Dioscorea alata).

Background and AimsInferring the diffusion history of many human-dispersed species is still not straightforward due to unresolved past human migrations. The centre of diversification and routes of migration of the autopolyploid and clonally propagated greater yam, Dioscorea alata, one of the oldest edible tubers, remain unclear. Here, we address yam demographic and dispersal history using a worldwide sample.MethodsWe characterized genome-wide patterns of genetic variation using genotyping by sequencing 643 greater yam accessions spanning four continents. First, we disentangled the polyploid and clonal components of yam diversity using allele frequency distribution and identity by descent approaches. We then addressed yam geographical origin and diffusion history with a model-based coalescent inferential approach.Key ResultsDiploid genotypes were more frequent than triploids and tetraploids worldwide. Genetic diversity was generally low and clonality appeared to be a main factor of diversification. The most likely evolutionary scenario supported an early divergence of mainland Southeast Asian and Pacific gene pools with continuous migration between them. The genetic make-up of triploids and tetraploids suggests that they have originated from these two regions before westward yam migration. The Indian Peninsula gene pool gave origin to the African gene pool, which was later introduced to the Caribbean region.ConclusionsOur results are congruent with the hypothesis of independent domestication origins of the two main Asian and Pacific gene pools. The low genetic diversity and high clonality observed suggest a strong domestication bottleneck followed by thousands of years of widespread vegetative propagation and polyploidization. Both processes reduced the extent of diversity available for breeding, and this is likely to threaten future adaptation.

A comparative assessment of diversity of greater yam (Dioscorea alata) in China

Dioscorea alata is a species of yam that is widely cultivated throughout the world, including China. Nevertheless, there is very limited knowledge on this type of yam diversity in China. In the present study, we assessed the genetic diversity of Chinese greater yam by analyzing their morphology, genotype, chromosome and ploidy. 142 cultivated greater yams were collected from eight geographical regions of China. 16 morphological characters were used for phenotypic variation assessment. Genotypic diversity was analyzed using 186 EST-SSR markers, while the chromosomes counting and ploidy evaluation were detected by flow cytometry. A broad morphological diversity was found, i.e. significant differences among accessions were found at each quantitative trait. The genetic similarity coefficients ranged from 0.42 to 0.91 with an average of 0.70. UPGMA and PCA indicated that the population was separated into two major clusters. The variation within pops accounted for 99.0%. 10 chromosome counts genotypes showed mainly 2n = 40, Da176 was a mixoploid with 20 and 40 chromosomes. Four levels of ploidy were detected by flow cytometry technology, and 87.3% of accessions had 40 chromosomes. Our findings demonstrated a broad variation of cultivated greater yam at phenotypic, genotypic and ploidy levels in two groups of observed cultivars.

Analysis of Biochemical Composition of Yams (Dioscorea spp.) Landraces from Southwest Ethiopia

Yams make a significant contribution to food security and medicinal importance in developing countries. In Ethiopia, there is insufficient scientific study on biochemical composition of Ethiopian yams. In order to fill the knowledge gap, this study was conducted to assess the biochemical composition of yams collected from Southwest Ethiopia. Flour from storage tuber of 36 yam landraces collected and the samples run in duplicates. Data on 14 biochemical traits were collected and subjected to various data analysis. Results of the analysis of variance indicated significant variation (p<0.01) among the landraces on organic matter, total nitrogen, protein, fat, carbohydrate, total phosphorus, total energy, tannin and saponin contents. The flour moisture contents ranged from 17.75 to 27.47% with a mean of 22.03%. The ranges of dry matter (15.80 to 27.28%), organic matter (21.38 to 43.56%), ash (1.13 to 3.56%), organic carbon (0.63 to 1.98 g), crude fiber (0.41 to 2.05%), total nitrogen (1.00 to 1.32%), protein (6.25 to 8.28%), fat (0.09 to 0.65%), carbohydrate (12.71 to 33.94%), total phosphorus (23.7 to 53.0 mg/100 g), total energy (92.66 to 173.30 kcal/100 g DM), tannin (19.80 to 181.0 mg/100 g) and saponin (2.31 to 13.94 mg/100 g) contents. The cluster and distance analysis of biochemical traits showed the existence of eight divergent groups. The maximum inter cluster distance was found between clusters VI and VII (133.59), followed by clusters V and VI (109.19), clusters II and VI (105.22), clusters I and VI (100.42), and clusters III and VI (89.25) in order of magnitudes. Maximum genetic divergence between the clusters points out the fact that hybridization among the landraces included with them would produce potential and meaningful hybrids and desirable segregants. Besides, investigation of the existed yam landraces based on molecular marker analysis is vital for better assessment of genetic diversity of yams in Ethiopia.

Crop wild relative conservation: Wild yams are not that wild

Extension of land use has been the main way to increase agricultural production to date. Natural habitats have consequently decreased and became increasingly fragmented, putting high pressure on the wild relatives of main crops. In this study, we assessed the diversity of wild relatives and cultivated varieties of yam, Dioscorea rotundata, a tuber crop grown in West Africa. Using nuclear markers, we showed that 19% of the wild plants were in fact hybrids between wild and cultivated varieties. Using whole chloroplast sequences, our results suggest that hybridization may be even stronger, with 43% of the wild individuals presenting either chloroplast or nuclear introgression with the cultivated yams. Adaptation of agriculture to current new pathogen outbreaks and ongoing climatic changes will require mining the vast diversity found in crops wild relatives. However, our study suggests that wild yam diversity is already largely tainted by crop-to-wild gene flow. The need to focus on in-situ wild yam conservation is even more crucial, since today, ex-situ genebanks contain nearly no wild yam accessions. Data profileMicrosatellite allele scoring is available as an online appendix; NGS data (.bam file) are available as SRA bioproject PRJNA383673.

Genetic diversity analysis in greater yam (Dioscorea alataL.) native to India using morphological and molecular markers

India holds a rich genetic diversity of yams and the occurrence of about fifty different Dioscorea species was reported, largely in the west, east and northeastern regions. Among the Dioscorea species, greater yam (Dioscorea alata L.) is the most important species grown throughout India. The National Repository on Tuber Crops Germplasm at Central Tuber Crops Research Institute, India conserves 431 accessions of greater yam as field gene bank. Wide variability for tuber shape, flesh colour, plant architecture and other morphological, biochemical and agronomic traits were recorded among accessions in the field gene bank. In the present study, morphological and molecular characterization was carried out in greater yam accessions collected from 14 states representing the major yam growing regions in India. A total of 48 morphological traits were recorded using International Plant Genetic Resources Institute (IPGRI) descriptors. Ten microsatellite markers were screened and seven polymorphic markers were used for molecular characterization. The results showed the divergence of the genotypes between southern states adjoining Western Ghats and north eastern states that form the two hot spots of biodiversity. Several triploids with high dry matter content (>35%) and compact tuber shape were isolated. This paper depicts the wide spectrum of variation present in greater yam native to India and its use in developing hybrids with value added traits. (Resume d'auteur)

Evolution and Phylogenetic Diversity of Yam Species (Dioscorea spp.): Implication for Conservation and Agricultural Practices.

Yams (Dioscorea spp.) consist of approximately 600 species. Presently, these species are threatened by genetic erosion due to many factors such as pest attacks and farming practices. In parallel, complex taxonomic boundaries in this genus makes it more challenging to properly address the genetic diversity of yam and manage its germplasm. As a first step toward evaluating and preserving the genetic diversity yam species, we use a phylogenetic diversity (PD) approach that has the advantage to investigate phylogenetic relationships and test hypotheses of species monophyly while alleviating to the problem of ploidy variation within and among species. The Bayesian phylogenetic analysis of 62 accessions from 7 species from three regions of Cameroon showed that most Dioscorea sections were monophyletic, but species within sections were generally non-monophyletic. The wild species D. praehensilis and cultivated D. cayenensis were the species with the highest PD. At the opposite, D. esculenta has a low PD and future studies should focus on this species to properly address its conservation status. We also show that wild species show a stronger genetic structure than cultivated species, which potentially reflects the management of the yam germplasm by farmers. These findings show that phylogenetic diversity is a promising approach for an initial investigation of genetic diversity in a crop consisting of closely related species.

English

A survey was conducted in four yam growing communities in southern Ghana, with the objectives of analyzing the diversity of yam species being cultivated, extent of production, yams preferred and identification of challenges confronting yam production. A total of 264 farmers were involved in the survey, 200 men and 64 women. Six yam species were encountered and 136 varieties were characterized according to the number of households cultivating the varieties, area under cultivation, frequency of harvesting and the preferred yams. Invariably in the four communities, most of the varieties were cultivated in small areas by few households, depicting serious genetic erosion of yams in the communities. Preference of yams cultivated depended mostly on the maturity period, ability to withstand biotic and abiotic stresses and multiple utilization as food sources. Eleven constraints were enumerated which needs to be addressed to ensure sustainable yam production. The inter-relations of the species with respect to the characteristics surveyed are presented. Key words: Yam diversity, genetic erosion, productivity, Ghana.

Varietal diversity and genetic erosion of cultivated yams (Dioscorea cayenensis Poir - D. rotundata Lam complex and D. alata L.) in Togo

Yam (Dioscorea cayenensis Poir - Dioscorea rotundata Lam complex; Dioscorea alata L.) is one of the major food crops that significantly contribute to food security and poverty alleviation in Togo. To assess its cultivar diversity and document the performence of existing cultivars vis-a-vis biotic and abiotic factors, 50 villages were randomly selected throughout the country and surveyed. The study reveals the existence of important diversity. The number of cultivars varied from 5 to 51 per village, with an average of 27. Central Region and Region of Plateau were the richest (31 to 37 cultivars on average per village) and the Savannah region, which is highly affected by climate change, was the poorest (7 cultivars on average per village). Based on vernacular names and subject to synonymy, 470 cultivars of D. cayenensis - D. rotundata complex and 134 cultivars of D. alata were identified. The spatial distribution of the diversity was established using Ordinary Kriging modelling approach. The rate of cultivar loss recorded per village was high (37.01% on average) and call for urgent definition of a national strategy to preserve yam diversity in Togo. Through participatory evaluation, the performances of the identified farmer-named cultivars were documented against 21 variables of which 12 were agronomic, three were technological and six were culinary. Very few tolerant or resistant varieties were identified per biotic and abiotic stress, indicating the urgent need to establish a national yam breeding program in Togo. This would help supply the different agroecological zones with performing varieties in relation to their needs. To clarify synonymies, exhaustive germplasm collections followed by morphological and molecular characterizations have been recommended. Key words: Cultivar loss, diversity, genetic erosion, participatory evaluation, spatial analysis, yam, Togo.

Genetic structure of farmer-managed varieties in clonally-propagated crops

The relative role of sexual reproduction and mutation in shaping the diversity of clonally propagated crops is largely unknown. We analyzed the genetic diversity of yam-a vegetatively-propagated crop-to gain insight into how these two factors shape its diversity in relation with farmers' classifications. Using 15 microsatellite loci, we analyzed 485 samples of 10 different yam varieties. We identified 33 different genotypes organized in lineages supported by high bootstrap values. We computed the probability that these genotypes appeared by sexual reproduction or mutation within and between each lineage. This allowed us to interpret each lineage as a product of sexual reproduction that has evolved by mutation. Moreover, we clearly noted a similarity between the genetic structure and farmers' classifications. Each variety could thus be interpreted as being the product of sexual reproduction having evolved by mutation. This highly structured diversity of farmer-managed varieties has consequences for the preservation of yam diversity.