Profiling Cultivars Development in Kersting's Groundnut [Macrotyloma geocarpum (Harms) Maréchal and Baudet] for Improved Yield, Higher Nutrient Content, and Adaptation to Current and Future Climates

Kersting's groundnut [Macrotyloma geocarpum (Harms.) Maréchal and Baudet], Fabaceae, is an important source of protein and essential amino acids. As a grain legume species, it also contributes to improving soil fertility through symbiotic nitrogen fixation. However, the crop is characterized by a relatively low yield (≤500 kg/ha), and limited progress has been made so far, toward the development of high-yielding cultivars that can enhance and sustain its productivity. Recently, there was an increased interest in alleviating the burdens related to Kersting's groundnut (KG) cultivation through the development of improved varieties. Preliminary investigations assembled germplasms from various producing countries. In-depth ethnobotanical studies and insightful investigation on the reproductive biology of the species were undertaken alongside morphological, biochemical, and molecular characterizations. Those studies revealed a narrow genetic base for KG. In addition, the self-pollinating nature of its flowers prevents cross-hybridization and represents a major barrier limiting the broadening of the genetic basis. Therefore, the development of a research pipeline to address the bottlenecks specific to KG is a prerequisite for the successful expansion of the crop. In this paper, we offer an overview of the current state of research on KG and pinpoint the knowledge gaps; we defined and discussed the main steps of breeding for KG' cultivars development; this included (i) developing an integrated genebank, inclusive germplasm, and seed system management; (ii) assessing end-users preferences and possibility for industrial exploitation of the crop; (iii) identifying biotic and abiotic stressors and the genetic control of responsive traits to those factors; (iv) overcoming the cross-pollination challenges in KG to propel the development of hybrids; (v) developing new approaches to create variability and setting adequate cultivars and breeding approaches; (vi) karyotyping and draft genome analysis to accelerate cultivars development and increase genetic gains; and (vii) evaluating the adaptability and stability of cultivars across various ecological regions.

Ecological-niche modeling of genetically distinct populations revealed Kersting’s groundnut [Macrotyloma geocarpum (Harms) Maréchal et Baudet] as a resilient orphan crop to present and future climates

Orphan legume crops play an important role in smallholder farmers’ food systems. Though less documented, they have the potential to contribute to adequate nutrition in vulnerable communities. Unfortunately, data are scarce about the potential of those crops to withstand current and future climate variations. Using Macrotyloma geocarpum as an example, we used genetically informed ecological niche models to explore the role of ecology on the current and future distributions of genetic populations of Kersting’s groundnut. Three main conclusions emerged: i) the models had good predictive power, indicating that M. geocarpum’s distribution was correlated with both climatic and soil layers; ii) identity and similarity tests revealed that the two genetic groups while overlapping, are each, locally adapted and display differences in climate suitability; iii) by integrating the genetic information in niche modeling, niches projections show divergence in the response of the species and genetic populations to ongoing climate change. This study highlights the importance of incorporating genetic data into ENM approaches to obtain a finer information of species’ future distribution, and explores the implications for agricultural adaptation, with a particular focus on identifying priority actions in orphan crops conservation and breeding.

Metabolite Fingerprinting of Kersting's Groundnut [Macrotyloma geocarpum (Harms) Maréchal & Baudet] Seeds Using UPLC-qTOF-MS Reveals the Nutraceutical and Antioxidant Potentials of the Orphan Legume

The identification and subsequent quantification of phenolic compounds in plants is the first step toward harnessing their associated nutritional and health benefits. Due to their diverse phenolic compound compositions, grain legumes are known for their high nutritional and health values. The aim of this study was to assess the inter-variations in chemical composition, phytochemical content, and antioxidant capacity of seed extracts from eight Kersting's groundnut [Macrotyloma geocarpum (Harms) Marechal & Baudet] landraces. The chemical profiles were evaluated using UPLC-qTOF-MS. Total phenolics and flavonoids content were determined by the Folin-Ciocalteu and aluminum chloride methods, respectively. The antioxidant capacities in the forms of DPPH and ABTS were evaluated using spectrophotometric methods. Principal component analysis was used to define similarities/differences between the landraces. Based on untargeted metabolomics analysis, 57 metabolites were identified, with phenolics, triterpenes, fatty acids, and sphingolipids being the most predominant. The results showed that the black seeded KG1 (Puffeun) had the highest total phenolic (9.44 mg GAE/g) and flavonoid (3.01 mg QE/g) contents, as well as antioxidant capacity (9.17 μg/mL and 18.44 μg/mL based on DDPH and ABTS assays, respectively). The concentrations of ferulic acid hexoside, procyanidin B2, eryodictyiol-7-rutinoside and quercetin pentoside ranged from 51.78–441.31, 1.86–18.25, 3.26–13.95 to 5.44–63.85 μg/mg, respectively. This study presents a useful report on the phytochemical characterization of Kersting's groundnuts and shows that the grains can be used as a source of nutraceuticals for human consumption.

Genetic Diversity and Population Structure in a Regional Collection of Kersting’s Groundnut (Macrotyloma geocarpum (Harms) Maréchal & Baudet)

Kersting’s groundnut is an important source of protein and essential nutrients that contribute to food security in West Africa. However, the crop is still underexploited by the populations and under-researched by the scientific community. This study aimed to investigate the genetic diversity and population structure of 217 Kersting’s groundnut accessions from five origins using 886 DArTseq markers. Gene diversity was low and ranged from 0.049 to 0.064. The number of private alleles greatly varied among populations (42–192) and morphotypes (40–339). Moderate to very high levels of selfing and inbreeding were observed among populations (s=56–85%, FIS=0.389–0.736) and morphotypes (s=57–82%, FIS=0.400–0.691). Moreover, little to very high genetic differentiations were observed among populations (0.006≤FIS≤0.371) and morphotypes (0.029≤FIS≤0.307). Analysis of molecular variance partitioned 38.5% of the genetic variation among and 48.7% within populations (P<0.001). Significant isolations by distance were detected between populations (R2=0.612, P=0.011) and accessions (R2=0.499, P<0.001). Discriminant analysis of principal components and neighbour joining consistently distinguished eight distinct clusters. These data provide a global picture of the existing genetic diversity for Kersting’s groundnut and will guide the choice of breeding strategies to increase production.

Quelques paramètres physiologiques et constituants biochimiques des organes de la lentille de terre (Macrotyloma geocarpum) en conditions de stress hydrique

La lentille de terre est une espèce en voie de disparition car sa culture demeure rudimentaire et traditionnelle. Aucun effort n’est fait pour améliorer cette culture. C’est pourquoi, elle n’occupe pas une place particulière en Afrique comme d’autres cultures vivrières. Ainsi, l’étude a consisté d’une part, à évaluer l’effet de stress sur le taux d’accumulation des composés biochimiques, et d’autre part, à évaluer les paramètres physiologiques et agronomiques dans les organes. Pour cela, 3 niveaux d’alimentation hydrique sont considérés : un stress hydrique sévère de 12 jours, un autre léger de 7 jours et une alimentation normale de 2 jours. L’expérimentation a été conduite en serre dans des pots avec un sol sablonneux. Un seul essai a été mis en place pour une durée de 125 jours. Des résultats obtenus, il ressort que le stress appliqué a perturbé sérieusement les plantes sous stress sévère. La chlorophylle est plus concentrée dans les feuilles des plantes stressées les rendant plus foncées. Un décalage de début de floraison et de cycle est observé chez les plantes stressées. Les plantes sévèrement stressées présentent des gousses de taille 2 fois plus grosses (3,5 cm) que celles des plantes témoins (1,8 cm). Les plantes stressantes ont des organes produisant une biomasse sèche plus faible que ceux des plantes témoins. Les taux des glucides et des protéines sont élevés dans les racines et les feuilles. L’étude a montré que la lentille de terre est riche en glucide et en protéine. Le stress a d’effet sur le rendement et la qualité des gousses. Il est judicieux d’envisager la mesure du degré de tolérance à la sécheresse.Mots clés : Déficit hydrique, organes, Macrotyloma geocarpum, taux d’accumulation, biomasse. English Title: Some physiological and constituent parameters biochemical of the bodies of the ground lens (Macrotyloma geocarpum) in conditions of hydrous stressThe duckweed is an endangered species because its culture remains rudimentary and traditional. No effort is made to improve this culture. This is why it does not occupy a special place in Africa like other food crops. Thus, the study consisted, on the one hand, of evaluating the effect of stress on the rate of accumulation of biochemical compounds, and on the other hand, of evaluating the physiological and agronomic parameters in the organs. For this, 3 levels of water supply are considered: a severe water stress of 12 days, another mild of 7 days and a normal water supply of 2 days. The experiment was carried out in a greenhouse in pots with sandy soil. A single trial was set up for a period of 125 days. From the results obtained, it appears that the stress applied has seriously disturbed plants under severe stress. Chlorophyll is more concentrated in the leaves of stressed plants, making them darker. A delayed start of flowering and cycle is observed in stressed plants. The severely stressed plants have pods twice as large (3.5 cm) as those of the control plants (1.8 cm). Stressful plants have organs producing a lower dry biomass than those of control plants. Carbohydrate and protein levels are high in the roots and leaves. The study showed that the ground lentil is rich in carbohydrates and proteins. Stress affects the yield and quality of the pods. It is a good idea to consider measuring the degree of drought tolerance.Keywords: Hydrous deficit, bodies, Macrotyloma geocarpum, rate of accumulation biomass.

Evaluation agro-morphologique de sept écotypes de lentille de terre (Macrotyloma geocarpum) cultivés au Burkina Faso

Macrotyloma geocarpum est une légumineuse dont sa culture est largement abandonnée au profit de celle d’autres légumineuses. Cette étude avait pour objectif d’identifier les écotypes performants à partir d’une caractérisation agromorphologique dans les conditions pluviales. Les résultats ont montré une diversité phénotypique entre les écotypes pour les caractères couleur du tégument, couleur des fleurs et du pétiole. L’analyse de variance a révélé une faible variabilité entre les caractères quantitatifs. La classification ascendante hiérarchique a mis en évidence 3 ensembles de diversité agro-morphologique. Le premier groupe constitué de 3 écotypes à graines noires, est caractérisé par un nombre important de feuilles trifoliolées à la floraison, un cycle du semis à la floraison intermédiaire et un poids de 100 bonnes graines élevé. Le second groupe compte un seul écotype à graines blanches, caractérisé par un cycle de floraison précoce, un nombre de feuilles trifoliolées faible et un poids de 100 bonnes graines faible. Le troisième groupe constitué de 3 écotypes à graines noires, est caractérisé par un cycle de floraison tardif, un nombre de feuilles trifoliolées moyen et un poids de 100 bonnes graines moyen. Ces résultats pourront contribuer à la création de variétés performantes répondant aux attentes des producteurs et consommateurs.Mots clés: Culture négligée, génotypes, caractères, variabilité, climat. English Title: Agro-morphological evaluation of seven earth lens (Macrotyloma geocarpum) ecotypes cultivated in Burkina FasoMacrotyloma geocarpum is a legume whose cultivation is largely abandoned in favor of that of other legumes. The objective of this study was to identify successful ecotypes based on agromorphological characterization in rainfed conditions. The results showed phenotypic diversity between the ecotypes for seed coat color, flower color and petiole color. Analysis of Variance revealed little variability between quantitative traits. The hierarchical ascending classification has highlighted 3 sets of agro-morphological diversity. The first group consisting of 3 black-seeded ecotypes is characterized by a large number of trifoliate leaves at flowering, a cycle of sowing at intermediate flowering and a high weight of 100 good seeds. The second group has only one white-seeded ecotype characterized by an early flowering cycle, a low trifoliate leaf count and a low good seed weight of 100. The third group of 3 black-seeded ecotypes is characterized by a late flowering cycle, a medium number of trifoliate leaves and a medium weight of 100 good seeds. These results can contribute to the creation of high-performance varieties that meet the expectations of producers and consumers.Keywords: Neglected crop, Genotypes, characters, variability, climate.

Farmers’ Preferences for Genetic Resources of Kersting’s Groundnut [Macrotyloma geocarpum (Harms) Maréchal and Baudet] in the Production Systems of Burkina Faso and Ghana

Pulses play important roles in providing proteins and essential amino-acids, and contribute to soils’ nutrients cycling in most smallholder farming systems in Sub-Saharan Africa (SSA). These crops can be promoted to meet food and nutrition security goals in low-income countries. Here, we investigated the status of Kersting’s groundnut (Macrotyloma geocarpum, Fabaceae), a neglected pulse in West Africa. We explored its diversity, the production systems, the production constraints and farmers’ preferences in Burkina Faso and Ghana. Focus groups and semi-structured interviews were conducted in 39 villages with 86 respondents grouped in five sociolinguistic groups. Our results indicated that Macrotyloma geocarpum was produced in three cultivation systems: in the first system, farmers grew Kersting’s groundnut in fields, mostly on mounds or on ridges; in the second system, farmers grew it as field border; and in the third system, no clear tillage practice was identified. The main constraints of those farming systems included: difficulty to harvest, the lack of manpower and the damage due to high soil humidity at the reproductive stage. A total of 62 samples were collected and clustered in six landraces based on seed coat colors including cream, white mottled with black eye, white mottled with greyed orange eye, black, brown mottled, and brown. All six groups were found in the southern-Sudanian zone whereas only white mottled with black eye and black colors were found in the northern-Sudanian zone. The white mottled with black eye landrace was commonly known and widely grown by farmers. Farmers’ preferences were, however, influenced by sociolinguistic membership and the most preferred traits included high yielding, drought tolerance, and resistance against beetles. These findings offer an avenue to develop a relevant breeding research agenda for promoting Kersting’s groundnut in Burkina Faso and Ghana.