Tribe Phaseoleae Research Articles

The complete chloroplast genome of Flemingia stricta Roxb. ex Ait. 1812 (Phaseoleae, Fabaceae)

Flemingia stricta Roxb. ex Ait. 1812 belongs to the Phaseoleae tribe within the Fabaceae family and has significant pharmaceutical value. In this study, we reported the complete chloroplast genome of F. stricta using the Illumina DNA sequencing data. The chloroplast genome was 152,940 bp and encoded 111 unique genes, including 77 protein-coding genes (PCGs), 30 transfer RNA (tRNA) genes, and 4 ribosomal RNA (rRNA) genes. The phylogenetic analysis confirmed that F. stricta was closely related to Flemingia prostrata and Flemingia macrophylla. The chloroplast genome of F. stricta could provide critical information for the molecular breeding of F. stricta and be used as a reference genome for other species of Phaseoleae.

Integrated morphological analysis of floral nectaries and androecia in the tribe Phaseoleae (Leguminosae, Papilionoideae)

Flowers of Leguminosae, the third largest angiosperm family, display outstanding diversity and are adapted to different modes of pollination. However, floral nectar is their most common and important reward. The morphology and position of the specialized floral nectaries (FNs) have been described only in the minority of legumes to date, so the investigation of these structures requires a further progress. The exact origin of these nectaries in legumes has been a matter of debate for more than a century. It was hypothesized that FNs are either of staminal origin or have no homology with any floral organs. This paper is devoted to the morphological study, using scanning electron microscopy (SEM), of the floral nectaries in seven taxa of the tribe Phaseoleae, with a focus on their localization, timing of their emergence, symmetry, along with a discussion of their possible identity. Some features of the androecium morphology potentially related to the interaction with pollinators were also studied. Although FNs have an annular habit in all studied species, they possess some features of monosymmetry, such as bilabiate shape or uneven distribution of secretory stomata. These FNs emerge late in ontogeny when all other floral parts are already differentiated and may be either free from other floral parts or adnate to the hypanthium. It is hypothesized that the leguminous FNs are not derived from stamens but represent structures sui generis although their spatial patterning is most probably dependent on some pentamerous floral whorl(s), i.e., a perianth or an androecium.

Deciphering the Plastomic Code of Chinese Hog-Peanut (Amphicarpaea edgeworthii Benth., Leguminosae): Comparative Genomics and Evolutionary Insights within the Phaseoleae Tribe.

The classification and phylogenetic relationships within the Phaseoleae tribe (Leguminosae) have consistently posed challenges to botanists. This study addresses these taxonomic intricacies, with a specific focus on the Glycininae subtribe, by conducting a comprehensive analysis of the highly conserved plastome in Amphicarpaea edgeworthii Benth., a critical species within this subtribe. Through meticulous genomic sequencing, we identified a plastome size of 148,650 bp, composed of 128 genes, including 84 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. Comparative genomic analysis across seven Glycininae species illuminated a universally conserved circular and quadripartite structure, with nine genes exhibiting notable nucleotide diversity, signifying a remarkable genomic variability. Phylogenetic reconstruction of 35 Phaseoleae species underscores the affinity of Amphicarpaea with Glycine, placing Apios as a sister lineage to all other Phaseoleae species, excluding Clitorinae and Diocleinae subtribes. Intriguingly, Apios, Butea, Erythrina, and Spatholobus, traditionally clumped together in the Erythrininae subtribe, display paraphyletic divergence, thereby contesting their taxonomic coherence. The pronounced structural differences in the quadripartite boundary genes among taxa with unresolved subtribal affiliations demand a reevaluation of Erythrininae's taxonomic classification, potentially refining the phylogenetic contours of the tribe.

COWPE BEAN PRODUCTION - (VIGNA UNGUICULATA (L.) WALP). A DROUGHT-RESISTANT PLANT IS VERY COMMON IN REGIONS OF THE BRAZILIAN SEMI-ARID

Cowpea is a dicotyledonous plant, originating from Africa, belonging to the order Fabales, Family Fabaceae, subfamily Faboideae, tribe Phaseoleae, subtribe Phaseolina, genus Vigna, species Vigna unguiculata (L.) Walp, the bean is considered a plant resistant to drought and is very common in regions of the Brazilian semi-arid region. It is commonly known as cowpea, macassar bean, black-eyed pea or green bean, among others. Given this, the objective of the present study was to carry out a bibliographical review of studies published in recent years to observe the nutritional potential and its economic viability for its production. The searches were carried out in Google Scholar databases. The harvested area of cowpea in the world is approximately 11,806,648 hectares, with a production of 5,389,235 tons, with Nigeria (2,916,00 tons) and Niger (1,265,839 tons) standing out among the largest producers. Cowpea production in Brazil is concentrated in the Northeast (1.2 million hectares) and North (55.8 thousand hectares) regions, predominantly cultivated in the semi-arid hinterland of the Northeast region, cowpea is cultivated in practically all micro-regions in the state of Paraíba, with a production of 62,018 tons in an area of 186,151 hectares, ranking fourth in planted area in the Northeast. The results show that cowpea has good energy and nutritional reserves that can be used in numerous recipes, including sautéed desserts, sweets, among others. Therefore, it presents itself as a very rich and nutritious food. A visit was made to some of Felipe Rodrigues Maia’s properties, in the rural community Sítio Cedro, with geographic coordinates of 37º57’20” longitude to the west and latitude to the south of 07º44’57”. It is located approximately four kilometers from the urban area of the municipality of Princesa Isabel - PB, to learn about the forms of production cultivation and the main pests that affect plantations in the semi-arid region and how to deal with this problem, as it is a factor Knowing its forms and how to deal with pests is crucial for cultivation. In view of what was obtained in the research, beans should be included in the human diet in a complementary way, considering that the crop is quite representative in the region where it plays an effective role in the population’s diet, as it constitutes an excellent source of low-cost proteins and carbohydrates.

The ricebean genome provides insight into Vigna genome evolution and facilitates genetic enhancement.

The ricebean genome provides insight into Vigna genome evolution and facilitates genetic enhancement.

First Report of Leaf Blight on Dumasia villosa Caused by Boeremia exigua in China.

Dumasia (Fabaceae, tribe Phaseoleae, subtribe Glycininae), a genus of trifoliate vines, is widely distributed in tropical and subtropical regions of Asia and Africa (Pan & Zhu 2010). In October 2021, lesions were observed on Dumasia villosa leaves on Longwen mountain of Guizhou Normal University, Guiyang City, Guizhou Province, China. The incidence of leaf blight on observed D. villosa leaves was 10%. All necrotic spots were close to insect-feeding sites. Necrotic spots were grey or black, and circular (2 to 10 mm in diameter) or irregular (2 to 20 mm long) in shape. Stems and pods showed no disease symptoms. Pathogen isolation was conducted following surface sterilization with ethanol. After growth for 5 days on potato dextrose agar in a moist climate chamber at 26°C under a 16 h/8 h light/dark cycle, colonies were 5.2 to 5.6 cm in diameter, olivaceous grey in colour, and sparse, white, aerial mycelia with irregular margins were evident. Conidia were hyaline, ellipsoidal to oblong, mostly 1-septate, and occasionally aseptate with dimensions ranging from 3.5 to 7.0 × 1.5 to 3.5 μm (n = 30). To confirm the species of the isolate, ribosomal DNA internal transcribed spacer (ITS) and β-tubulin (tub2) genes were amplified and sequenced using primers ITS1/ITS4 and Btub2Fd/Btub4Rd (White et al. 1990), respectively. The obtained 529 bp ITS sequence (GenBank accession no. OL872186) shares 99.61% identity with the sequences of Boeremia exigua (MF662797 and GU395499). The obtained 299 bp tub2 sequence (OM830712) shares 100% identity with the sequence of B. exigua (KR653201). Based on morphology and DNA sequence analysis, the isolate was identified as B. exigua. To fulfil Koch's postulates, healthy leaves of 8-week-old D. villosa plants (n = 6) were wounded with a sterilized hypodermic needle and inoculated with 2 μL of a conidial suspension (106 conidia/mL). Six plants were inoculated with 2 μL of sterile distilled water as controls. After 3 days in a moist climate chamber at 26°C under a 16 h/8 h light/dark cycle, dark spots were only present on conidia-inoculated leaves, while controls remained healthy. Boeremia exigua was reisolated from disease spots and confirmed using the same morphological and molecular methods described above. To our knowledge, this is the first report of leaf blight on D. villosa caused by B. exigua, although this fungus has been reported to infect leguminous plants, including field pea (Li et al. 2012), white clover (Wang et al. 2020), and soybean (Schaffrath et al. 2020). In China, B. exigua has also been reported to infect other plants, such as walnut (Cai et al. 2021; Wang et al. 2021) and Japanese ginseng (You et al. 2015). This identification suggests that D. villosa could be a potential reservoir for the pathogen affecting other leguminous crops that might be economically important.

Effect of Soil Amendments with Botanical Leaves on Root-Knot Nematode (Meloidogyne incognita) of Cowpea (Vigna unguiculata L.)

Cowpea (Vigna unguiculata L. Walp) is a earliest crop which is a member of the Phaseoleae tribe of the Leguminosae Family widely known as Lobia, which is a better alternative source for protein, minerals etc., as compared to other legumes. Root-knot nematodes (Meloidogyne incognita) cause a major loss in cowpea production by hindering nutrient and water uptake. Leaf waste of marigold, rose, calotropis, euphorbia, neem and castor as botanical amendments were experimented under field conditions during kharif 2021 for their effectiveness against the root knot nematodes, rhizobium nodule and growth parameters. Field studies were conducted in randomized blocks with six treatments and three replications. Among the composts, the treatment Neem leaf compost remarkably increased the Plant height at 90 DAS (293 cm), root length at 90 DAS (29.16cm), rhizobium nodules (5), and significantly decreased the root weight at 90 DAS (3.5 gm) and root knots in the root system of cowpea at 90 DAS (10.67). The weight of the roots decreased because of a decrease in the number of root knot in cowpea compared to other composts and control T0.

Comparative cytogenomics reveals genome reshuffling and centromere repositioning in the legume tribe Phaseoleae.

The tribe Phaseoleae includes several legume crops with assembled genomes. Comparative genomic studies have evidenced the preservation of large genomic blocks among legumes, although chromosome dynamics during Phaseoleae evolution has not been investigated. We conducted a comparative genomic analysis to define an informative genomic block (GB) system and to reconstruct the ancestral Phaseoleae karyotype (APK). We identified GBs based on the orthologous genes between Phaseolus vulgaris and Vigna unguiculata and searched for GBs in different genomes of the Phaseolinae (P. lunatus) and Glycininae (Amphicarpaea edgeworthii) subtribes and Spatholobus suberectus (sister to Phaseolinae and Glycininae), using Medicago truncatula as the outgroup. We also used oligo-FISH probes of two P. vulgaris chromosomes to paint the orthologous chromosomes of two non-sequenced Phaseolinae species. We inferred the APK as having n = 11 and 19 GBs (A to S), hypothesizing five chromosome fusions that reduced the ancestral legume karyotype to n = 11. We identified the rearrangements among the APK and the subtribes and species, with extensive centromere repositioning in Phaseolus. We also reconstructed the chromosome number reduction in S. suberectus. The development of the GB system and the proposed APK provide useful approaches for future comparative genomic analyses of legume species.

Regulation of flavonoid biosynthesis in representatives of the tribe Phaseoleae DC.

Flavonoids play a crucial role in plant metabolism. Many of them have antioxidant activity, and they are also pigments that render a variety of colors to plant tissues. Foods rich in flavonoid compounds are considered as functional components of a healthy diet. Currently, there is an increased interest in studying genetic mechanisms underlying the coloration of plants. Flavonoid biosynthesis pathways are controlled by two groups of genes. Structural genes encode enzymes, while regulatory genes are responsible for transcription factors that activate the expression of structural genes. Transcription factors that belong to R2R3-Myb, bHLH-Myc and WDR families form the ternary MBW complex, which is involved in regulating the expression of structural genes of flavonoid biosynthesis. The mechanisms of regulation of the anthocyanins and proanthocyanidin biosynthesis by the MBW complex are described in detail for the model plant Arabidopsis thaliana L. This review summarizes data on the regulation of phenolic pigment biosynthesis and the features of phenolic pigment accumulation in plant tissues in the main representatives of the Phaseoleae tribe: soybean Glycine max (L.) Merr., common bean Phaseolus vulgaris L., adzuki bean Vigna angularis (Willd.) Ohwi & Ohashi, and cowpea V. unguiculata (L.) Walp. The species discussed in this review are the most important food legumes in many countries of the world and they comprise the staple food in diets of millions of people. Identification and characterization of the genes controlling the flavonoid biosynthesis pathways are necessary for successful breeding of modern varieties with an increased dietary value. Identification of the flavonoid accumulation patterns is essential for solving the problem of broadening the diversity of plant products.

Structural organization of <em>TFL1</em>-like genes in representatives of the tribe Phaseoleae DC.

The type of stem growth is one of the key features in determining plant architectonics. Stem growth type is an economically important trait. It interconnects with stem length, flowering duration, yield, resistance to lodging, and suitability of mechanized cultivation. Mutations in the TFL1 gene and its homologs have been demonstrated to change meristem indeterminacy across genera. The aim of this work was to characterize and compare the structural organization of TFL1-like genes in representatives of the tribe Phaseoleae (pigeonpea Cajanus cajan, soybean Glycine max, common bean Phaseolus vulgaris, adzuki bean Vigna angularis, mung bean V. radiata, and cowpea V. unguiculata) based on in silico analysis, including analysis of nucleotide sequences, predicted elements in promoter regions, predicted amino acid sequences, putative functional domains and 3D protein structures. We investigated TFL1 (one gene for adzuki bean, four copies for soybean, two copies for other studied species), ATC (two copies for soybean, one gene for other investigated species), and BFT (two copies for soybean, one gene for other studied species) gene family members found in whole-genome sequences databases available for representatives of the tribe Phaseoleae. The presence of duplicated copies for all genes in soybean may be a result of the last genome duplication event during the evolution of this species. Duplication of TFL1 gene to two copies in most of studied species of the tribe Phaseoleae is probably accompanied by the maintenance of the functional state of these genes. The exception is VrTFL1.2 of V. radiata, which likely had lost its functionality. This work broadens the existing data about the number of gene copies, their structural divergence and evolution, and the expected functional differences. This information will be important for understanding the molecular genetic mechanisms underlying the maintenance of indeterminacy in the growth of the shoot apical meristem, as well as in the control of the transition to the reproductive phase of plant development.

<p><strong><em>Millettia lantsangensis</em></strong><strong> is conspecific with <em>Cruddasia insignis</em> (Fabaceae)</strong></p>

Millettia lantsangensis Z.Wei was described within the tribe Millettieae on the basis of one fruiting and two flowering gatherings from Yunnan Province, China. Our critical examination shows that these gatherings are mixed and represent two distinct species from two different tribes. The fruiting specimens have woody branches, terminal infructescences and inflated pods, closely resembling Callerya sphaerosperma (Z. Wei) Z. Wei & Pedley from the same tribe, while the flowering collections have soft and herbaceous branches, axillary pseudoracemes and wart-like brachyblasts, and belong to Cruddasia insignis Prain from the tribe Phaseoleae. Because one of the flowering specimens was indicated as the type of Millettia lantsangensis, this is here reduced to a synonym of Cruddasia insignis. The genus Cruddasia Prain was previously reported only from Myanmar and Thailand, and is therefore a new genus record for the flora of China.

Molecular phylogeny and character evolution of Flemingia (Leguminosae, Papilionoideae, Phaseoleae, Cajaninae) inferred from three cpDNA and nrITS sequence data

The genus Flemingia belonging to the family Leguminosae (Papilionoideae, Phaseoleae, Cajaninae) comprises ca. 30–35 species and is distributed mainly in tropical and subtropical Africa, Asia and Oceania. Previous systematic studies of the genus Flemingia were based on morphology only, or aimed at reconstructing relationships, delimiting distinct evolutionary lineages based on morphological and molecular data, focusing on its allied genera or the tribe Phaseoleae as a whole and thus included a limited sampling of the genus Flemingia. In this present study, phylogeny of Flemingia was inferred from molecular data of three cpDNA plastid markers (matK, rps16-trnQ, and psbA-trnH) and one nuclear region (nrITS) of 73 accessions representing ca. 31 species and all five previously recognized infrageneric groups (subgenus/section) of Flemingia. Results revealed the para- and polyphyly of four previously recognized subgenera/sections within the genus Flemingia, the exception for the group Lepidocoma. Our nuclear phylogeny recovered four major clades and one single species clade, F. faginea. This species was, however, grouped in clade III (Ostryodium group) in chloroplast phylogeny. Incongruence between the trees of chloroplast and nuclear markers may point to either introgression or incomplete lineage sorting. Furthermore, the evolution of three major morphological features in Flemingia was discussed. The results of this research are not in the favor of synonymization of F. glutinosa with F. lineata, and F. ferruginea, F. cumingiana, F. phillipinensis, F. latifolia, F. prostrata, F. stricta, F. wallichi, F. grahamiana, F. sootepensis with F. macrophylla.

The First Genetic Map for a Psoraleoid Legume (Bituminaria bituminosa) Reveals Highly Conserved Synteny with Phaseoloid Legumes.

We present the first genetic map of tedera (Bituminaria bituminosa (L.) C.H. Stirton), a drought-tolerant forage legume from the Canary Islands with useful pharmaceutical properties. It is also the first genetic map for any species in the tribe Psoraleeae (Fabaceae). The map comprises 2042 genotyping-by-sequencing (GBS) markers distributed across 10 linkage groups, consistent with the haploid chromosome count for this species (n = 10). Sequence tags from the markers were used to find homologous matches in the genome sequences of the closely related species in the Phaseoleae tribe: soybean, common bean, and cowpea. No tedera linkage groups align in their entirety to chromosomes in any of these phaseoloid species, but there are long stretches of collinearity that could be used in tedera research for gene discovery purposes using the better-resourced phaseoloid species. Using Ks analysis of a tedera transcriptome against five legume genomes provides an estimated divergence time of 17.4 million years between tedera and soybean. Genomic information and resources developed here will be invaluable for breeding tedera varieties for forage and pharmaceutical purposes.

Taxonomic significance of vegetative and reproductive morphology in southern Africa Rhynchosia sect. Rhynchosia (Fabaceae: Papilionoideae, Phaseoleae)

Rhynchosia is the largest genus in the subtribe Cajaninae, tribe Phaseoleae. Due to the lack of a recent taxonomic revision in the genus, the species are poorly known and as a result, are difficult to identify. As part of our ongoing taxonomic studies on the genus in southern Africa, this paper presents a comparative study of vegetative and floral morphological variation in the 47 species currently recognised in the type section Rhynchosia in the region. This is with a view to provide useful diagnostic morphological characters that can be used to correctly identify species in the type section and in other sections. The study used morphological data from field observation, herbarium specimens, and literature. Stems, leaves, and floral structures were examined with a dissecting microscope. A stereoscope with a camera lucida attachment was used to draw the reproductive morphology. Although morphological characters seem to overlap between the sections, characters such as leaflets size, type of indumentum on leaflet surfaces, stipules shape, type and length of inflorescences, presence or absence of indumentum on standard petals, presence and absence of sculpturing on wing petals, as well as length of upper lobes of the calyx are useful in identifying species.

Diversity of repetitive sequences within compact genomes of Phaseolus L. beans and allied genera Cajanus L. and Vigna Savi.

Repetitive sequences are ubiquitous and fast-evolving elements responsible for size variation and large-scale organization of plant genomes. Within tribe Phaseoleae (Fabaceae), some genera, such as Phaseolus, Vigna, and Cajanus, show small genome and mostly stable chromosome number. Here, we applied a combined computational and cytological approach to study the organization and diversification of repetitive elements in some species of these genera. Sequences were classified in terms of type and repetitiveness and the most abundant were mapped to chromosomes. We identified long terminal repeat (LTR) retrotransposons, especially Ogre and Chromovirus elements, making up most of genomes, other than P. acutifolius and Vigna species. Satellite DNAs (SatDNAs) were less representative, but highly diverse among species, showing a clear phylogenetic relationship. In situ localization revealed preferential location at pericentromeres and centromeres for both types of sequences, suggesting a heterogeneous composition, especially for centromeres. Few elements showed subterminal accumulation. Copy number variation among chromosomes within and among species was observed for all nine identified SatDNAs. Altogether, our data pointed two main elements (Ty3/Gypsy retrotransponsons and SatDNAs) to the diversification on the repetitive landscape in Phaseoleae, with a typical set of repeats in each species. The high turnover of these sequences, however, did not affect total genome size.

Taxonomic notes on the genus Neorautanenia (Fabaceae–Phaseoleae)

Background: Neorautanenia is a small genus in the subtribe Glycininae within the tribe Phaseoleae in the family Fabaceae. It is distributed in southern and Tropical Africa. Historically, the genus is known to consist of three species, namely, N. brachypus, N. ficifolia and N. mitis; morphological data suggest that these should be reduced to two.Objectives: The aim of this article is to formally sink N. brachypus into the synonymy of N. mitis and to provide the correct typification, diagnostic features, diagnostic key, distribution maps, as well as illustrations of the morphological features of the two species.Methods: Observations were made on herbarium specimens housed at PRE. Morphological features were studied and measurements of characters recorded.Results: Neorautanenia mitis is extremely variable morphologically, so that several authors recognised many different variants, some of these as distinct species, including N. brachypus. Examination of numerous specimens, however, indicates that these are merely morphological and/or geographical variants of N. mitis. This observation prompted Verdcourt to place this taxon as a synonym of N. mitis; however, he reversed that decision 30 years later. It has become necessary to revert to the original decision.Conclusions: Neorautanenia brachypus is formally reduced to a synonymy of N. mitis and as a result the genus comprises only two species.

Characteristics of the exine and aperture of pollen grains of Eriosema and Rhynchosia (Leguminosae – Papilionoideae – Phaseoleae)

The genera Eriosema and Rhynchosia, which comprise approximately 150 and 230 species, respectively, belong to the tribe Phaseoleae and to the subtribe Cajaninae. The pollen morphology of 49 species of Eriosema and 13 of Rhynchosia were studied using scanning electron microscopy to identify diagnostic characteristics that could aid in the taxonomic circumscription of those genera. The pollen grains analysed were obtained from specimens deposited in the BOTU, CEPEC, IPA, HRB, HUEFS, OUPR, P, S, UFC, and UFRJ herbaria. The species studied demonstrated that the pollen grains dispersed in monads, are isopolar or heteropolar, triporate or tricolporate, angulaperturate; with the endo-aperture membrane generally psilate and the exine largely reticulate heterobrocate, except for R. claussenii which is microreticulate. We discuss these diverse characteristics, including the ornamentation of the endo-aperture membrane and the margins of the apertures and reticula, to obtain information that possibly could be used to differentiate between the two genera. Although this proved not to be possible using pollen, because many characters overlap between the two genera, nevertheless some species display unique, taxonomically useful, characters, such as R. platyphylla which has an apocolpium in the shape of a ‘Y’, E. bauchiense with a verrucate exine ornamentation, and E. benthamianum with fossulate lumina. Additionally, two pollen types were identified in Eriosema, one group of species with 3-porate pollen grains and the other composed of species with 3-colporate grains.

Assessing legumes indigenous to South Africa, Lesotho and Swaziland for their pasture potential

In contrast to the exploration and use of southern African grass plant genetic resources over the past century, only a few indigenous legume species are currently used as forages, notwithstanding the vast untapped legume diversity available in southern Africa. The aim of this study was to assess legumes, indigenous to South Africa, Lesotho and Swaziland and propose a list of species with pasture potential for further evaluation. Towards this end, legume species documented as being cultivated, grazed or browsed as well as plant collection data from the National Herbarium, South Africa, were used. The majority of cultivated, grazed or browsed species were recorded in the Central Bushveld, Lowveld and Mopane Bioregions, the Drakensberg Foothill and Coastal Region, Savanna Group and Northern Mistbelt leguminochoria and is largely enclosed by the Wolkberg Centre of Plant Endemism. The Phaseoleae tribe was found to contain the highest percentage of cultivated legume species. Legume species adapted to low soil phosphorus levels were identified, with 22 of these species previously noted for their pasture potential. It is suggested that the results of this study be used in the continued search for alternative indigenous legumes species for eventual integration into local and international pasture systems.

Revisiting the Leaflet Secretory Structures in Subtribe Cajaninae Benth. (Leguminosae, Phaseoleae)

Premise of research. Cajaninae is the most speciose subtribe of the legume tribe Phaseoleae, comprising ca. 490 species distributed in 10 genera. The group is characterized by peculiar secretory st...

A transcriptome-SNP-derived linkage map of Apios americana (potato bean) provides insights about genome re-organization and synteny conservation in the phaseoloid legumes

Key messageWe report a linkage map for Apios americana and describe synteny with selected warm-season legumes. A translocation event in common bean and soybean is confirmed against Apios and Vigna species.Apios (Apios americana; “apios”), a tuberous perennial legume in the Phaseoleae tribe, was widely used as a food by Native Americans. Work in the last 40 years has led to several improved breeding lines. Aspects of the pollination biology (complex floral structure and tripping mechanism) have made controlled crosses difficult, and the previous reports indicated that the plant is likely primarily an outcrosser. We used a pseudo-testcross strategy to construct a genetic map specific to the maternal parent. The map was built using single-nucleotide polymorphism markers identified by comparing the expressed sequences of individuals in the mapping population against a de novo maternal reference transcriptome assembly. The apios map consists of 11 linkage groups and 1121 recombinationally distinct loci, covering ~ 938.6 cM. By sequencing the transcriptomes of all potential pollen parents, we were able to identify the probable pollen donors and to discover new aspects of the pollination biology in apios. No selfing was observed, but multiple pollen parents were seen within individual pods. Comparisons with genome sequences in other species in the Phaseoleae showed extended synteny for most apios linkage groups. This synteny supports the robustness of the map, and also sheds light on the history of the Phaseoleae, as apios is relatively early diverging in this tribe. We detected a translocation event that separates apios and two Vigna species from Phaseolus vulgaris and Glycine max. This apios mapping work provides a general protocol for sequencing-based construction of high-density linkage maps in outcrossing species with heterogeneous pollen parents.