Genetic Diversity and Environmental Influence on Growth and Yield Parameters of Bambara Groundnut

Exploiting genetic and genomic resources to enhance productivity and abiotic stress adaptation of underutilized pulses

Underutilized pulses and their wild relatives are typically stress tolerant and their seeds are packed with protein, fibers, minerals, vitamins, and phytochemicals. The consumption of such nutritionally dense legumes together with cereal-based food may promote global food and nutritional security. However, such species are deficient in a few or several desirable domestication traits thereby reducing their agronomic value, requiring further genetic enhancement for developing productive, nutritionally dense, and climate resilient cultivars. This review article considers 13 underutilized pulses and focuses on their germplasm holdings, diversity, crop-wild-crop gene flow, genome sequencing, syntenic relationships, the potential for breeding and transgenic manipulation, and the genetics of agronomic and stress tolerance traits. Recent progress has shown the potential for crop improvement and food security, for example, the genetic basis of stem determinacy and fragrance in moth bean and rice bean, multiple abiotic stress tolerant traits in horse gram and tepary bean, bruchid resistance in lima bean, low neurotoxin in grass pea, and photoperiod induced flowering and anthocyanin accumulation in adzuki bean have been investigated. Advances in introgression breeding to develop elite genetic stocks of grass pea with low β-ODAP (neurotoxin compound), resistance to Mungbean yellow mosaic India virus in black gram using rice bean, and abiotic stress adaptation in common bean, using genes from tepary bean have been carried out. This highlights their potential in wider breeding programs to introduce such traits in locally adapted cultivars. The potential of de-domestication or feralization in the evolution of new variants in these crops are also highlighted.

Yield response of accessions of Bambara groundnut (Vigna subterranea (L) Verdc) inoculated with Bradyrhizobium japonicum strains

Field experiments were conducted in two different agroecological locations of Ibadan and Ikenne in Nigeria from August through December during the 2019 and 2020 cropping seasons. The studies were set up to reduce reliance on inorganic nitrogen fertilizer and to embrace the use of nitrogen-fixing bacteria to improve legume production to increase farmers' output and profitability. Ten accessions of the Bambara groundnut (BGN) were used in the trials. Seeds of each BGN accession were coated with each of the following Bradyrhizobium japonicum strains (B. japonicum): FA3, RACA6, USDA110, and IRJ2180A before planting. Furthermore, Nitrogen (N) fertilizer (20 kg/ha, urea) was applied to seedlings without inoculation, and uninoculated seedlings (without inoculation and without fertilization) served as control. The experiment was, therefore, a factorial arrangement (10 BGN accessions, 4 B. japonicum strains, N fertilizer application, and an uninoculated control). The yield and yield components of the inoculated BGN accessions were significantly enhanced at both agroecological locations and seasons. Among the B. japonicum strains used for inoculation, RACA6 strains significantly enhanced the yield and yield component of TVSu-1698 than other inoculated BGN accessions with a mean value of 6,234 ± 87 kg ha−1 recorded in both locations and seasons, compared to the result obtained in the combination of TVSu-1698 with N fertilizer with a mean value of 3,264 ± 943 kg ha−1. By using TVSu-1698 with RACA6 strain, farmers can get 85% more yield than on average with other genotypes/strains combination, while an average yield of 60% could be obtained by farmers using N fertilizer application.

Genetic variation and characterization of Bambara groundnut [Vigna subterranea (L.) verdc.] accessions under multi-environments considering yield and yield components performance

Bambara groundnut has significant role to play in terms of food security, even though researchers in agriculture have paid very little attention to the crop in the past. This study aimed to investigate the high-yielding accessions in three environments. A total of 34 phenological, vegetative and yield traits were measured and analyzed statistically with R software. There were significant differences in all the traits except for plant height, initial plant stand, panicle length per stem, and petiole length. Across the three environments, TVSU-455 gave the highest values for the total number of pods (42.67), final plant stands (7.67), fresh seed weights (45.83), number of seeds per plant (46.62), hundred seed weight with a value (124.56), dry seed weight (27.14), fresh pod weight (92.65), harvest index of 0.57, yield per plot (45.83) and unshelled yield per plot (550.26). TVSU-455 was the only accession in cluster I of the dendrogram based on its superiority over other accessions. The clustering analysis produced a dendrogram categorizing the 15 accessions into 4 groups based on the vegetative, phenological, and yield traits. There were significant differences among the correlations of the 34 traits. The first two principle components explained 56.16% of the total variation with each dimension accounting for 39.85% and 16. 31% variation, respectively. TVSU-455 can be recommended for stability analysis.

Variations of Nutrient and Antinutrient Components of Bambara Groundnut (Vigna subterranea (L.) Verdc.) Seeds

Bambara groundnut (BGN) fits the bill when it comes to an acceptable level of nutrient and mineral composition. BGN is a balanced food that can help eradicate food and nutritional insecurity if it is incorporated into the major food system. However, there is a large degree of variation in nutrient composition and antinutritional factors among BGN accessions. Here, we show the degree of variability of nutrient and antinutrient components such as percentage ash, moisture, protein, fat, tryptophan, tannin, and phytate contents in seeds of 95 accessions of BGN. Data were subjected to analysis of variance (ANOVA), followed by correlation and principal component analysis. Clustering was done to show the relatedness between the accessions in response to the various traits. A high level of heterogeneity was observed among the accessions for the various traits studied. PC1 and PC2 show 41.2% of the total observed variations. Cluster analysis grouped accessions into four main clusters. This study was able to confirm the high level of diversity in the components of nutrients and antinutrients previously reported in BGN. The results of this study are expected to aid in identifying parent lines for improved breeding programs.

Plant growth-promoting rhizobacteria for orphan legume production: Focus on yield and disease resistance in Bambara groundnut

Orphan legumes are now experiencing growing demand due to the constraints on available major food crops. However, due to focus on major food crops, little research has been conducted on orphan legumes compared to major food crops, especially in microbiome application to improve growth and yield. Recent developments have demonstrated the enormous potential of beneficial microbes in growth promotion and resistance to stress and diseases. Hence, the focus of this perspective is to examine the potential of plant growth promoting rhizobacteria (PGPR) to improve Bambara groundnut yield and quality. Further insights into the potential use of PGPR as a biological control agent in the crop are discussed. Finally, three PGPR genera commonly associated with plant growth and disease resistance (Bacillus, Pseudomonas, and Streptomyces) were highlighted as case studies for the growth promotion and disease control in BGN production.

Unveiling Genetic Diversity, Characterization, and Selection of Bambara Groundnut (Vigna subterranea L. Verdc) Genotypes Reflecting Yield and Yield Components in Tropical Malaysia

Addressing genetic diversity and application of appropriate breeding strategies are imperative for Bambara groundnut (Vigna subterranea L.) improvement as a newly introduced legume in Malaysia. It has become a “miracle lucrative” legume for Asia and Africa because of its drought resilience, excellent nutritional profiles, and versatile uses. This crop's progress has been limited owing to a lack of extensive research, marginalization, inadequate knowledge, and a lack of accessible funds, among other concerns. The expansion of this crop is reliant on the assessment and selection of unique and reliable breeding lines in various circumstances. Consequently, the goal of this work is to determine genetic diversity and the relationship between yield-contributing components in 44 Bambara groundnut accessions sourced from the Genebank of Institute of Tropical Agriculture and Food Security (ITAFoS) at Universiti Putra Malaysia (UPM). Three replications were used in the experiment, which was done using a randomized complete block design (RCBD). The data were subjected to ANOVA, PCA, correlation, and heat map cluster analysis; also, genetic parameters and broad-sense heritability estimation were carried out on recorded phenotypic descriptors. All of the investigated variables had a significant variance (p ≤ 0.05 or 0.01) according to the ANOVA results. Yield per hectare showed a positively strong to perfect significant correlation (0.75 ≤ r ≤ 1.00; p ≤ 0.01) with the yield components viz. fresh pod weight, hundred seed weight, dry pod weight, and dry seed weight. Interestingly, these traits had heritability ≥ 60% and genetic gain ≥ 20%, which can be beneficial for direct selection to this crop improvement. The UPGMA clustering revealed five distinct clusters in which genotypes under cluster I, cluster II, and cluster IV produce a greater yield of 5.96%, 7.12%, and 15.05%, respectively, than the grand mean yield of 1927.01 kg/ha. The PCA biplot estimated that PC1 (32.9%) and PC2 (12.9%) would cover 45.8% of the total variance. We discovered 30 promising lines that provide yields per hectare more than 1.8 ton/ha and might be used as parental lines in future breeding operations aimed at improving the grain yield in tropical areas or comparable agroecological zones.

Genetic Diversity and Environmental Influence on Yield and Yield-Related Traits of Adzuki Bean (Vigna angularis L.)

Adzuki beans are an important food legume crop in East Asia. A large number of adzuki bean accessions are maintained in the Chinese national seed genebank. A collection of 59 elite cultivars, 389 landraces, and 27 wild adzuki beans were selected and phenotyped extensively for yield and yield-related traits at two different locations (Nanning and Nanyang, China). Ten agronomic and yield-related traits were scored, and the data were subjected to analysis of variance (ANOVA), principal component analysis (PCA), correlation, and cluster analysis. Significant variation was observed for genotypes, locations, and genotype x environment interaction for most traits. Also, there were significant differences in the phenotypes among accessions of different germplasm types. The broad-sense heritability of traits studied ranged from 4.4% to 77.8%. The number of seeds per pod (77.8%), 100-seed weight (68.0%), and number of plant branches (63.9%) had a high heritability. A total of 10 traits were transformed into 3 comprehensive factors by principal component analysis, and the first three principal component factors contributed 72.31% of the total variability. Cluster analysis categorized the 475 adzuki bean accessions into five distinct groups. The results described in this study will be useful for adzuki bean breeders for the development of varieties with high end-use quality.

Plant Growth Stage Drives the Temporal and Spatial Dynamics of the Bacterial Microbiome in the Rhizosphere of Vigna subterranea

Bambara groundnut (BGN) is an underutilized legume commonly found in sub-Saharan Africa. It thrives in marginal soils and is resistant to drought stress. Several studies have been carried out on the nutritional properties of BGN, but very little is known about the effects of plant growth changes and development on rhizosphere bacterial dynamics and function. This study reports on the bacterial dynamics and function in the bulk and rhizosphere soils of BGN at different growth stages (vegetative, flowering, pod-filling, and maturation stages). Aside from the maturation stage that shows distinct community structure from the other growth stages, results obtained showed no significant differences in bacterial community structure among the other growth stages. At a closer level, Actinobacteria, Proteobacteria, and Acidobacteria were dominant in rhizosphere soils at all growth stages. The bulk soil had the least average phyla abundance, while the maturity stage was characterized by the highest average phyla abundance. Rubrobacter, Acidobacterium, and Skermanella were the most predominant genus. It was observed from the analysis of operational taxonomic units that there was significant change in the bacterial structure of the rhizosphere with a higher abundance of potential plant growth-promoting rhizobacteria, at the different growth stages, which include the genera Bacillus and Acidobacterium. Biomarker analysis revealed 7 and 4 highly significant bacterial biomarkers by linear discriminant analysis effect size and random forest analysis at the maturation stage, respectively. The results obtained in this study demonstrated that the bacterial communities of BGN rhizosphere microbiome dynamics and function are influenced by the plant’s growth stages.

Improving Bambara Groundnut Production: Insight Into the Role of Omics and Beneficial Bacteria

With the rise in the world population, environmental hazards caused by chemical fertilizers, and a decrease in food supply due to global climate change, food security has become very pertinent. In addition, considerable parts of agriculture lands have been lost to urbanization. It has therefore been projected that at the present rate of population increase coupled with the other mentioned factors, available food will not be enough to feed the world. Hence, drastic approach is needed to improve agriculture output as well as human sustainability. Application of environmentally sustainable approach, such as the use of beneficial microbes, and improved breeding of underutilized legumes are one of the proposed sustainable ways of achieving food security. Microbiome-assisted breeding in underutilized legumes is an untapped area with great capabilities to improve food security. Furthermore, revolution in genomics adaptation to crop improvement has changed the approach from conventional breeding to more advanced genomic-assisted breeding on the host plant and its microbiome. The use of rhizobacteria is very important to improving crop yield, especially rhizobacteria from legumes like Bambara groundnut (BGN). BGN is an important legume in sub-Saharan Africa with high ability to tolerate drought and thrive well in marginalized soils. BGN and its interaction with various rhizobacteria in the soil could play a vital role in crop production and protection. This review focus on the importance of genomics application to BGN and its microbiome with the view of setting a potential blueprint for improved BGN breeding through integration of beneficial bacteria.