Search

The hexaploid sweetpotato is one of the most important root crops worldwide. However, its genetic origins remain controversial. In this study, we identified two likely progenitors of sweetpotato by analyzing the horizontally transferred IbT-DNA and a haplotype-based phylogenetic analysis. The diploid form of I. aequatoriensis contributed the B1 subgenome, the IbT-DNA2 and the lineage 2 type of the chloroplast genome to sweetpotato. The tetraploid progenitor of sweetpotato is I. batatas 4x, donating the B2 subgenome, IbT-DNA1 and the lineage 1 type of chloroplast genome. Sweetpotato is derived from reciprocal crosses between the diploid and the tetraploid progenitor, and a subsequent whole genome duplication. We also detected biased gene exchanges between subgenomes. The B1 to B2 subgenome conversions were almost 3-fold higher than the B2 to B1 subgenome conversions. This study sheds lights on the evolution of sweetpotato and paves the way for the improvement of the crop.

Stable and sufficient food supplies are increasingly threatened by climatic variability, in particular extreme heat events. Intraspecific crop diversity may be an important biological resource to both understand and maintain crop resilience to extreme conditions. Here using data from a mass field experiment screening for heat tolerance in sweet potato (Ipomoea batatas), we identify 132 heat-tolerant cultivars and breeding lines (6.7%) out of 1,973 investigated. Sweet potato is the world's fifth most important food crop, and mean conditions experienced by sweet potato by 2070 are predicted to be 1 to 6 °C warmer, negatively impacting most genotypes. We identify canopy temperature depression, chlorophyll content and storage root-flesh colour as predictors of heat tolerance and, therefore, as potential traits for breeding consideration. These results highlight the role of intraspecific biodiversity for the productivity and resilience of food and agricultural systems in the face of climate change.

The hexaploid sweet potato is one of the most important root crops worldwide. However, its genetic origins, especially that of its tetraploid progenitor, are unclear. In this study, we conceived a pipeline consisting of a genome-wide variation-based phylogeny and a novel haplotype-based phylogenetic analysis (HPA) to determine that the tetraploid accession CIP695141 of Ipomoea batatas 4x from Peru is the tetraploid progenitor of sweet potato. We detected biased gene exchanges between subgenomes. The B1 to B2 subgenome conversions were almost 3-fold higher than the B2 to B1 subgenome conversions. Our analyses revealed that the genes involved in storage root formation, sugar transport, stress resistance, and maintenance of genome stability have been selected during the speciation and domestication of sweet potato. This study sheds lights on the evolution of sweet potato and paves a way for the improvement of sweet potato.

Sweet potato (Ipomoea batatas, Lam.) is an important root vegetable in developing countries. After its domestication in Neotropical America, human migration led to the distribution of the sweet potato plant throughout the world. Both leaf and storage root are high in compounds of nutritional value. Yet, the storage roots are of particular value due to their significant content of provitamin A (β-carotene). The breeding effort for elite sweet potato lines led to the reduction of genetic diversity and the potential to improve other traits. The focus of the present study was to assess the metabolic diversity of 27 sweet potato cultivars including landraces and improved varieties. A metabolite profiling approach was optimised for sweet potato leaf and storage root tissue and 130 metabolites identified with three different analysis platforms. The data highlighted a lack of correlation between storage root phenotype and leaf metabolism. Furthermore, the metabolic diversity of storage roots was based on the secondary metabolism, including phenylpropanoids and carotenoids. Three cultivars of three different flesh colouration (yellow, orange and purple) showed a significant difference of the primary metabolism. This data demonstrates the value of metabolite profiling to breeding programs as a means of identifying differences in phenotypes/chemotypes and characterising parental material for future pre-breeding resources., Food crops: Assessing the metabolic diversity of sweet potato Understanding the metabolic variations of different types of sweet potato could help improve their nutritional value. Sweet potato is one of the world’s major food crops but recurrent breeding of high yielding lines is reducing their genetic diversity. A study led by Paul D. Fraser, Royal Holloway University of London, UK, examined the chemical differences between 25 types of sweet potato, including orange and purple varieties. They show that there is little correlation between the chemicals found in the leaves and storage root material and that there are significant differences in metabolism between varieties that produce different pigments in their storage roots. Their findings highlight the importance of metabolite profiling for identifying those varieties that produce the highest levels of starch and health-promoting compounds such as carotenoids.

The goal of yam bean improvement in Africa is to develop superior high yielding and high dry matter cultivars that are preferred for adoption. In this study, the estimates of variance components, heritability and response to selection were studied in F3 yam bean families selected from interspecies crosses targeting improvement of storage root dry matter and associated traits. Breeding populations were generated using North Carolina II (NC II) mating design involving high dry matter P. tuberosus chuin cultivar, low dry matter P. ahipa and the high yielding P. erosus yam beans. The progenies were advanced through selfing from F1 to F2 population and then exposed to selection at 10% selection intensity to obtain 83 high dry matter lines. The selected lines were evaluated in an F3 trial using a randomized complete block design (RCBD) with three replications at the National Crops Resources Research Institute (NaCRRI) Namulonge, in Central Uganda. The results revealed significant (P P

Summary Roots, tubers, and bananas (RTB) are vital staples for food security in the world's poorest nations. A major constraint to current RTB breeding programmes is limited knowledge on the available diversity due to lack of efficient germplasm characterization and structure. In recent years large‐scale efforts have begun to elucidate the genetic and phenotypic diversity of germplasm collections and populations and, yet, biochemical measurements have often been overlooked despite metabolite composition being directly associated with agronomic and consumer traits. Here we present a compound database and concentration range for metabolites detected in the major RTB crops: banana (Musa spp.), cassava (Manihot esculenta), potato (Solanum tuberosum), sweet potato (Ipomoea batatas), and yam (Dioscorea spp.), following metabolomics‐based diversity screening of global collections held within the CGIAR institutes. The dataset including 711 chemical features provides a valuable resource regarding the comparative biochemical composition of each RTB crop and highlights the potential diversity available for incorporation into crop improvement programmes. Particularly, the tropical crops cassava, sweet potato and banana displayed more complex compositional metabolite profiles with representations of up to 22 chemical classes (unknowns excluded) than that of potato, for which only metabolites from 10 chemical classes were detected. Additionally, over 20% of biochemical signatures remained unidentified for every crop analyzed. Integration of metabolomics with the on‐going genomic and phenotypic studies will enhance ’omics‐wide associations of molecular signatures with agronomic and consumer traits via easily quantifiable biochemical markers to aid gene discovery and functional characterization., Significance Statement A metabolite‐specific database cataloguing the biochemical diversity within and between root, tuber, and banana (RTB) crops has been compiled from profiling thousands of accessions. The database records the extent of metabolite concentrations available in screened germplasm of each RTB crop and therefore can be used to set breeding targets. This information aids in crop breeding programmes to improve the livelihoods for more than two billion people reliant on RTB crops.

Crop diversity contributes to yield stability and nutrition security and is valued for its potential use in breeding improved varieties and adaptation to future climates. Women across the globe contribute to biodiversity conservation, and, in the Central Andes region, the cradle of potato diversity, rural women play a vital role in the management of a wealth of native potato diversity. To examine how gender roles and traditions influence the agricultural and conservation practices of male and female custodians of native potato diversity, we undertook a qualitative study in eight farming communities high in the Andes, in the Pasco region of Peru. This article reviews agricultural and crop diversity management practices, farmer motivations for conserving potato diversity, the role that agrobiodiversity plays in family diets and economies, and support of in situ conservation by external actors. It examines how gender norms limit the potential of women to fully benefit from the crop and argues for more gender-responsive approaches that empower both women and men, enable women to overcome barriers, and contribute to a more inclusive, community-based management of agrobiodiversity that ensures its long-term conservation and contribution to community development and well-being.

The CGIAR Research Program (CRP) on Roots, Tubers and Bananas (RTB) includes vegetatively propagated staple crops linked by common breeding, seed, and postharvest issues, and by the frequency with which women are involved in their production and use. RTB crops are the backbone of food security across the humid tropics in sub-Saharan Africa (SSA) and in more localized areas of Asia and Latin America. Around 300 million poor people in developing countries currently depend on RTB value chains for food security, nutrition and income. Climate change poses challenges which could undo progress in poverty reduction and markedly increase food insecurity. This article examines planning and research for climate resilience across RTB crops, with a particular focus on the contrasting potato and sweet potato cases in SSA. A six-step framework for climatesmart breeding is proposed: (1) downscaling climate change models and crop modeling; (2) identifying and understanding key climate change responsive traits; (3) breeding and varietal selection; (4) phenotyping and genomic research to accelerate gains; (5) developing management options for climate-smart varieties; and (6) deployment (seed systems). In summary, climate-smart breeding means we need to do what we already do but faster, better, and smarter.

Yam beans (Pachyrhizus DC.) are legume root crops that have attracted scientific interest because of high contents of starch, protein, and iron in their roots. In this study, 58 accessions of three cultivated Pachyrhizus species were characterized by amplified fragment length polymorphism (AFLP) molecular markers in order to estimate genetic diversity and interspecific relationships. To complement molecular marker information, individuals from each accession were analyzed in order to confirm ploidy levels. Eight AFLP primer combinations detected 136 (68.7 %) polymorphic bands. Shannon’s diversity indices (Hs) for each species were 1.04 (P. ahipa), 1.07 (P. tuberosus), and 2.42 (P. erosus), while the total diversity index was 2.45. Phylogenetic analysis, principal coordinate analysis and analysis of molecular variance (F ST = 0.796) all showed significant species differentiation. All accessions were diploid (2n = 2x = 22), which is characteristic of the tribe Phaseoleae. Finally, a misclassified accession of P. tuberosus was identified. Molecular characterization of accessions is necessary for efficient management of germplasm collections.

Understanding the distribution of crop genetic diversity in relation to environmental factors can give insights into the eco‐evolutionary processes involved in plant domestication. Yam beans (Pachyrhizus Rich. ex DC.) are leguminous crops native to South and Central America that are grown for their tuberous roots but are seed‐propagated. Using a landscape genetic approach, we examined correlations between environmental factors and phylogeographic patterns of genetic diversity in Pachyrhizus landrace populations. Molecular analyses based on chloroplast DNA sequencing and a new set of nuclear microsatellite markers revealed two distinct lineages, with strong genetic differentiation between Andean landraces (lineage A) and Amazonian landraces (lineage B). The comparison of different evolutionary scenarios for the diversification history of yam beans in the Andes using approximate Bayesian computation suggests that Pachyrhizus ahipa and Pachyrhizus tuberosus share a progenitor‐derivative relationship, with environmental factors playing an important role in driving selection for divergent ecotypes. The new molecular data call for a revision of the taxonomy of Pachyrhizus but are congruent with paleoclimatic and archeological evidence, and suggest that selection for determinate growth was part of ecophysiological adaptations associated with the diversification of the P. tuberosus–P. ahipa complex during the Mid‐Holocene.

Random amplified polymorphic DNA markers (RAPD) were used to assess the genetic relatedness among accessions of four species of Desmodium and allied genera (Dendrolobium triangulare, Desmodium gangeticum, Desmodium heterocarpon ssp. heterocarpon, and Tadehagi triquetrum) originating from Northeast Vietnam. Since information on the genetic diversity of these species is deficient, the creation of baseline data is an important means for the development of more sustainable and cost-efficient conservation approaches which eventually result in more comprehensive ex situ germplasm collections. The species analyzed are native to tropical and subtropical Asia, Australia, and Oceania and possess a potential as forage and/or medicinal plants. Moderate levels of inter-accession diversity represented by 37.5% and 33.3% of polymorphic fragments (P%) and average Jaccard's similarity coefficients (JSCs) of 0.60 and 0.64 were found in D. heterocarpon and T. triquetrum, respectively, while moderate to high levels were detected in D. triangulare (P% = 52.9 and JSC = 0.61) and D. gangeticum (P% = 34.5 and JSC = 0.49). Mantel tests failed to reveal a correlation between geographic and genetic distances. Based on the results of this study, baseline data for further marker-assisted research are generated and future collecting and ex situ conservation strategies for the species studied are discussed.

Crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas] have the potential to contribute to breeding objectives for this important root crop. Uncertainty in regard to species boundaries and their phylogenetic relationships, the limited availability of germplasm with which to perform crosses, and the difficulty of introgression of genes from wild species has constrained their utilization. Here, we compile geographic occurrence data on relevant sweetpotato wild relatives and produce potential distribution models for the species. We then assess the comprehensiveness of ex situ germplasm collections, contextualize these results with research and breeding priorities, and use ecogeographic information to identify species with the potential to contribute desirable agronomic traits. The fourteen species that are considered the closest wild relatives of sweetpotato generally occur from the central United States to Argentina, with richness concentrated in Mesoamerica and in the extreme Southeastern United States. Currently designated species differ among themselves and in comparison to the crop in their adaptations to temperature, precipitation, and edaphic characteristics and most species also show considerable intraspecific variation. With 79% of species identified as high priority for further collecting, we find that these crop genetic resources are highly under-represented in ex situ conservation systems and thus their availability to breeders and researchers is inadequate. We prioritize taxa and specific geographic locations for further collecting in order to improve the completeness of germplasm collections. In concert with enhanced conservation of sweetpotato wild relatives, further taxonomic research, characterization and evaluation of germplasm, and improving the techniques to overcome barriers to introgression with wild species are needed in order to mobilize these genetic resources for crop breeding.

Pueraria montana var. lobata and P. phaseoloides originating from tropical Asia and parts of Oceania are ecologically and economically important legumes that are used as green manure, cover crop or forage plants. Conservation and use of plant genetic resources require an understanding of the extent and distribution of genetic diversity in any given region. In this study, genetic variation of five P. montana var. lobata and 16 P. phaseoloides accessions was analysed developing a random amplified polymorphic DNA (RAPD) marker methodology for Pueraria species and thereby creating basic data for follow-up research and the development of conservation strategies. Seeds were collected from native populations in Bac Kan Province, a mountainous region in Northeast Vietnam. P. montana var. lobata presented a high level of variation with 54.3% of the detected markers being polymorphic, whereas P. phaseoloides exhibited an intermediate to high level of variation (45.5%). The P. montana var. lobata accessions clustered in congruence with their eco-geographical origin. For P. phaseoloides no correspondence between sampling sites and genetic differentiation was found. Inter-population differentiation was measured as Jaccard's similarity coefficient (JSC). Mean JSC amounted to 0.35 in P. montana var. lobata and 0.52 in P. phaseoloides. Results are compared to other genetic studies of herbaceous legumes and conservation strategies are suggested.

Flemingia macrophylla (Willd.) Kuntze ex Merr., a multi-purpose legume with potential as dry-season forage crop, mainly occurs in subhumid to humid environments of tropical and subtropical Asia. Despite increasing interest in conservation of germplasm suitable for low-input production systems information on the genetic diversity of F. macrophylla is extremely scarce. The creation of baseline data is supposed to contribute to more efficient conservation management and to identify collecting strategies of novel germplasm. Random amplified polymorphic (RAPD) markers were used to investigate the genetic variation among 37 F. macrophylla accessions. Germplasm analysed in this study originated from Bac Kan province, Northeast Vietnam. Eight primers generated a total of 47 amplified RAPD loci of which 38 were polymorphic. Jaccard’s similarity coefficients among accessions ranged from 0.069 to 1 with a mean of 0.67. The UPGMA dendrogram revealed three clusters along with three outliers. No correspondence between geographic and genetic distance was found (Mantel test: R = 0.21; P = 0.016). Analysis of molecular variance (AMOVA) revealed significant (P < 0.001) differentiation between accessions collected in lowland and upland regions. Results of UPGMA clustering were confirmed by the pattern of principle coordinates analysis (PCO) plotting. Future collecting strategies should target populations at large distances and along the altitudinal range. Ex situ conservation should encompass those accessions that showed genetic divergence. In situ conservation may consist of establishing a system of interconnected population fragments to guarantee continuing genetic exchange via corridors and of rehabilitating degraded habitats.

Yam bean (Pachyrhizus spp.) comprises three closely related cultivated species: P. ahipa grown locally in the Andean highlands, P. tuberosus grown throughout the Amazon Basin and P. erosus grown in Central America and Asia. The objectives of this study were to determine gene actions, combining ability and genetic parameters for earliness in F1 (P. ahipa × P. tuberosus) hybrids under Rwandan East African highland conditions. Three P. ahipa accessions (early maturing, tropical highlands) as females and three accessions of P. tuberosus (late maturing and high yields) as males were crossed using a North Carolina II mating design. Evaluation of F1 progeny and their parents revealed highly significant differences among crosses. Significant (P

In 2010, yam beans in a field trial in Peru showed viral disease symptoms. Graft-transmission and positive ELISA results using potyvirus-specific antibodies suggested that the symptoms could be the result of a potyviral infection. Small interfering RNA (siRNA) were extracted from one of the samples and sent for high-throughput sequencing. The full genome of a new potyvirus could be assembled from the resulting siRNA sequences, and it was sufficiently different from other sequences to be considered a member of a new species, which we have designated Yam bean mosaic virus (YBMV). Sequence similarity suggests that YBMV has also been detected in yam beans in Indonesia.

Crop wild relatives have a long history of use in potato breeding, particularly for pest and disease resistance, and are expected to be increasingly used in the search for tolerance to biotic and abiotic stresses. Their current and future use in crop improvement depends on their availability in ex situ germplasm collections. As these plants are impacted in the wild by habitat destruction and climate change, actions to ensure their conservation ex situ become ever more urgent. We analyzed the state of ex situ conservation of 73 of the closest wild relatives of potato (Solanum section Petota) with the aim of establishing priorities for further collecting to fill important gaps in germplasm collections. A total of 32 species (43.8%), were assigned high priority for further collecting due to severe gaps in their ex situ collections. Such gaps are most pronounced in the geographic center of diversity of the wild relatives in Peru. A total of 20 and 18 species were assessed as medium and low priority for further collecting, respectively, with only three species determined to be sufficiently represented currently. Priorities for further collecting include: (i) species completely lacking representation in germplasm collections; (ii) other high priority taxa, with geographic emphasis on the center of species diversity; (iii) medium priority species. Such collecting efforts combined with further emphasis on improving ex situ conservation technologies and methods, performing genotypic and phenotypic characterization of wild relative diversity, monitoring wild populations in situ, and making conserved wild relatives and their associated data accessible to the global research community, represent key steps in ensuring the long-term availability of the wild genetic resources of this important crop.