GGE biplot analysis of genotype x environment interaction and yield stability in bambara groundnut

Open Access Journal; Published online: 14 Sep 2021In plant breeding and agricultural research, biplot analysis has become an important statistical technique. The goal of this study was to find the winning genotype(s) for the test settings in a part of the Southwest region of Nigeria, as well as to investigate the nature and extent of genotype × environment interaction (GEI) effects on Bambara groundnut (BGN) production. The experiment was carried out in four environments (two separate sites, Ibadan and Ikenne, for two consecutive years, 2018 and 2019) with ninety-five BGN accessions. According to the combined analysis of variance over environments, genotypes and GEI both had a substantial (p < 0.001) impact on BGN yield. The results revealed that BGN accessions performed differently in different test conditions, indicating that the interaction was crossover in nature. The results revealed that BGN accessions performed differently in different test conditions, indicating that the interaction was crossover in nature. To examine and show the pattern of the interaction components, biplots with the genotype main effect and genotype × environment interaction (GEI) were used. The first two PCs explained 80% of the total variation of the GGE model (i.e., G + GE) (PC1 = 48.59%, PC2 = 31.41%). The accessions that performed best in each environment based on the “which-won-where” polygon were TVSu-2031, TVSu-1724, TVSu-1742, TVSu-2022, TVSu-1943, TVSu-1892, TVSu-1557, TVSu-2060, and TVSu-2017. Among these accessions, TVSu-2017, TVSu-1557, TVSu-2060, TVSu-1892, and TVSu-1943 were among the highest-yielding accessions on the field. The adaptable accessions were TVSu-1763, TVSu-1899, TVSu-2019, TVSu-1898, TVSu-1957, TVSu-2021, and TVSu-1850, and the stable accessions were TVSu-1589, TVSu-1905, and TVSu-2048. In terms of discriminating and representativeness for the environments, Ibadan 2019 is deemed to be a superior environment. The selected accessions are recommended as parental lines in breeding programs for grain yield improvement in Ibadan or Ikenne or similar agro-ecological zones

Morphological characterisation of selected African accessions of bambara groundnut (Vigna subterranea (L.) verdc.)

Open Access ArticleThree hundred (300) accessions of Bambara groundnut (Vigna subterranea (L.) Verdc) among the 1973 maintained in the global repository at the International Institute of Tropical Agriculture (IITA), Ibadan, genebank were selected for this study. Two to three seeds of each accession were planted during the 2014 / 2015 planting season at IITA, Ibadan, Nigeria. Seedlings were thinned to a single plant prior to flowering. Thirty - seven (37) agro-morphological parameters, representing 28 quantitative and 9 qualitative traits were recorded on each plant (IPGRI, 2000). The data were subjected to analysis using the statistics application system (SAS) software, version 9.3, both to depict correlation among parameters and eigen values with principal component on scree plot and dendrogram construction. The results revealed lines (e.g TVSu – 293, TVSu – 395, TVSu – 1243) that had high yield potentials. Also, TVSu -397 and TVSu – 1168 had the highest number of leaves while TVSu – 520 and TVSu – 1022 had the least. The least number of seeds per plant was given by TVSu – 1, TVSu – 353 and TVSu – 454, while TVSu – 395, TVSu – 618 and TVSu – 1897 gave the highest number of seeds at harvest. The result provides information necessary for future nutrition and breeding studies on Bambara groundnut and its improvement

Genetic diversity and environmental influence on growth and yield parameters of Bambara groundnut

Open Access Journal; Published online: 20 Dec 2021Bambara groundnut (BGN) is a drought-tolerant crop majorly cultivated in sub-Saharan Africa. Due to a lack of extensive research, marginalization, lack of awareness, and lack of available fund among others, this crop's improvement has been limited. The development of this crop depends on evaluation and selection of unique and stable breeding lines in different environments. This study aims to estimate genetic diversity using morphological traits at different locations in 95 accessions of BGN collected from the Genebank of the International Institute of Tropical Agriculture (IITA), Ibadan. The experiment was carried out in three replicates at IITA experimental sites in two agroecological zones in Ibadan (7°40′19.62″ N, 3°91′73.13″ E) and Ikenne (6°51′00.873″ N, 3°41′48.528″ E) using a randomized complete block design. Ten vegetative growth traits and eight yield traits were scored. The data was subjected to ANOVA, PCA, correlation, and cluster analysis. Estimations of genetic parameters and broad sense heritability were carried out on the traits. ANOVA revealed significant variation in each trait except for days to emergence. Significant variation was also observed for accession and location interactions (genotype x environment interactions) for plant height, leaf length, leaf width, chlorophyll content, number of petioles, germination count, number of pods, number of seeds, seed length, seed width, and yield. PC1 and PC2 show 42.3% of the total variations observed by the PC, with seed thickness contributing more to PC1 and the number of seeds contributing more to PC2. Cluster analysis categorized the accessions into four distinct groups. The number of pods had the highest genotypic coefficient of variation of 32.55% and the phenotypic coefficient of variation of 97.61%, while seed length (0.63), seed width (0.54), and seed thickness (0.58) have high heritability values. The genetic advance was highest in yield (76.15%) and lowest in days to 50% germination (0.21%). This study can be used to predict appropriate agroecological zones for the planting of BGN while the knowledge of the diversity of the accessions based on the traits could serve a guide in selecting the best trait for the improvement of the crop

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

Open Access JournalField 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

Preliminary assessment of the association between DArT-SEQ SNP and some nutritional traits in African yam bean

Open Access Article; Published online: 30 Nov 2020African yam bean (AYB) is an underutilized tropical legume rich in protein and starch content. This study's aim was to use Diversity Arrays Technology (DArT) sequencing to study the ge-nome-wide association studies (GWAS) of nutritional traits. The study was carried out on 137 accessions in IITA, Ibadan. Seeds were harvested at maturity and analysed for protein, oil, and starch using Kjeltec, Soxtec, and Phenol-sulfuric acid assay method. Mixed Linear Model (MLM) was used for GWAS analysis by employing the TASSEL software. AYB protein content ranged from 17.13-27.15%, while the oil and starch content ranged from 0.74-2.27% and 60.58-69.84%, respectively. A total of 3.6K SNP was generated using a high-throughput DArTseq genotype-by-sequencing SNP approach in the AYB population. These generated SNPs were filtered for quality control, and the remaining useful 2.48K SNPs were used for the preliminary GWAS. We identified a promising source of genetic material for important grain nutritional traits that could be used in AYB breeding research. Identification of QTL/gene of protein, oil, and starch will contribute to our understanding of the genetic basis of natural variation in AYB grain nutritional traits

Potential of genomics for the improvement of underutilized legumes in sub-Saharan Africa

Open Access Journal; Published online: 03 Jan 2021Underutilized, or orphan legumes, are widely distributed across farming landscapes in sub-Saharan Africa (SSA) but often have low yields and do not fulfill their potential due to very limited research, breeding, development, marketing, and awareness of their benefits. These advantages include nutritional quality and climate resilience. In this review, we focus on Bambara groundnut, African yam bean, and Kersting's groundnut. Knowledge of the challenges and rewards of exploiting them will provide opportunities for concerted approaches to their revival and contribution to future global food systems, especially in the context of climate change. This review identifies the institutional and noninstitutional challenges, the constraints, the prospects, and the rewards that can be derived from exploiting orphan legumes in SSA. The genetic resources center (GRC) of the International Institute of Tropical Agriculture (IITA) conserves a diverse collection of about 2500 accessions of these crops with the majority from Africa. In this review, we focus on the ex situ conservation of the genetic resources of these indigenous African legume crops, their characterization and evaluation, prospects for the development of improved cultivars, and the role they could play, particularly with respect to nutrition and adaptation to climate change. We emphasize progress made in recent years concerning the assembly of information required for application of genomics tools to these crops and how this will underpin the development of improved varieties

Assessment of yield stability of bambara groundnut (Vigna subterranea (L.) Verdc.) using genotype and genotype-environment interaction biplot analysis

Open Access JournalBiplot analysis has emerged as a crucial statistical method in plant breeding and agricultural research. The objective of this research was to identify the best-performing genotype(s) for the environments in three distinct regions of Nigeria while also examining the characteristics and magnitude of genotype–environment interaction (GEI) effects on the yield of Bambara groundnut (BGN). The study was conducted in Ibadan, Ikenne, and Mokwa, utilizing a sample of 30 accessions. The yield of BGN was found to be significantly affected by accessions, environment, and their interaction through a combined analysis of variance, with a p-value < 0.001. Biplots were utilized to demonstrate the pattern of interaction components, specifically the genotype’s main effect and genotype–environment interaction (GEI). The initial two principal components elucidated the complete variance of the GGE model, encompassing both genetic and genotype-by-environment interaction effects (PC1 = 87.81%, PC2 = 12.19%). The accessions that exhibited superior performance in each respective environment, as determined by the “which-won-where” polygon, were identified as TVSu-2223, TVSu-2236, TVSu-2240, and TVSu-2249 in Mokwa; TVSu-2214 in Ikenne; and TVSu-2188 in Ibadan. The accessions TVSu-2207 and TVSu-2199 exhibited stability in all environments, whereas the accessions TVSu-2226, TVSu-2249, TVSu-2209, TVSu-2184, TVSu-2204, and TVSu-2236 demonstrated adaptability. In addition, the accessions TVSu-2240 and TVSu-2283 were stable and adaptable in all environments. The accessions that were chosen have been suggested as suitable parental lines for breeding programs aimed at enhancing grain yield in the agro-ecological zones that were evaluated. This study’s findings identify BGN accessions with adaptability and stability across selected environments in Nigeria, suggesting specific accessions that can serve as suitable parental lines in breeding programs to enhance grain yield, thereby holding promise for improving food security

Genome-wide association analysis of phenotypic traits in Bambara groundnut under drought-stressed and non-stressed conditions based on DArTseq SNP

Open Access JournalIntroduction: Bambara groundnut (BG) (Vigna subterranea [L.] Verdc) is an indigenous, resilient, but underutilized leguminous crop that occurs mostly as genetically heterogeneous landraces with limited information on the drought tolerant attributes. This study elucidates the associations between sequencing-based diversity array technology (DArTseq) and phenotypic character as well as differing indices related to drought tolerance in one hundred accessions of Bambara groundnut. Methods: The field experiments were conducted at IITA research stations in Kano and Ibadan between 2016 and 2018 planting seasons. The experiments were arranged in randomised complete block design with three replications, under the different water regimes. The phenotypic traits evaluated was further to construct the dendrogram. Genome-wide association mapping was conducted based on 5927 DArTs loci with < 20% missing data. Results and Discussions: The genome wide association study predicted drought tolerance in Bambara accessions for geometric mean productivity (GMP) and stress tolerance index (STI). TVSu-423 had the highest GMP and STI values (28.50, 2.40), while TVSu-2017 had the lowest at GMP (1.74) and STI (0.01) respectively. The relative water content (%) was significantly higher for accessions; TVSu-266 (60.35, 61.49), TVSu-2 (58.29, 53.94), and TVSu-411 (55.17, 58.92) in 2016/2017 and 2017/2018, respectively. The phenotypic characters studied delineated the accessions into two major clusters and five distinct sub-clusters, indicating variations across all the geographical locations. The 5,927 DArTseq genomic markers in association with STI further grouped the 100 accessions into two main clusters. TVSu-1897 from Botswana (Southern Africa) was in the first cluster, while the remaining 99 accessions from Western, Central, and Eastern Africa made up the second cluster. The eight significant Quantitative Trait Loci (QTLs) (24346377|F|0-22:A>G-22:A>G, 24384105|F|0-56:A>G33 :A> G, 24385643|F|0-53:G>C-53:G>C, 24385696|F|0-43:A>G-43:A>G, 4177257|F|0-44:A>T-44:A>T, 4182070|F|0-66:G>A-66:G>A, 4183483|F|0-24:G>A-24:G>A, 4183904|F|0-11:C>T-11:C>T) identified with Bonferroni threshold was in association with STI, indicative of variations under the drought-stressed condition. The observation of consistent SNPs in the 2016 and 2017 planting seasons, as well as in combination with the 2016 and 2017 planting seasons, led to the designation of these QTLs as significant. The drought selected accessions could form basis for hybridization breeding. The identified quantitative trait loci could be useful in marker-assisted selection in drought molecular breeding programs

Genetic diversity and population structure of some Nigerian accessions of Bambara groundnut (Vigna subterranea (L.) Verdc.,) using DArT SNP markers

Open Access Article; Published online: 24 Sep 2022Bambara groundnut is one of the crops with inadequate molecular research to show its full potentials. Previous studies showed morphological diversity with inadequate information to confirm genetic variations. In the quest to reveal the genetic potentials, deoxyribonucleic acid (DNA) of the selected accessions was extracted through leaf samples at 3 weeks old, using Dellaporta Miniprep for Plant DNA Isolation procedure. The high quality DNA was sequenced using Diversity Arrays Technology (DArT) markers to unlock diversity among Bambara groundnut of Nigerian origin. Cluster analysis (neighbor-joining clustering) of the single nucleotide polymorphisms (SNP’s) were used to generate sub-population to show relatedness and differences. Seven sub-populations were generated with 5927 (50.13%) high quality DArT markers out of the 11,821 SNPs generated. This revealed high genetic diversity existed among the selected Bambara groundnut accessions in Nigeria. This also revealed that DArT markers were highly efficient in classifying the accessions based on molecular expressions. This study also identified markers responsible for genetic variation that could facilitate the characterization of larger collections for further utilization of genetic resources and most importantly Bambara groundnut for the purpose of crop improvement

Introgression breeding in cowpea [Vigna unguiculata (L.) walp.]

The narrow base of genetic diversity characteristic of cowpea can be attributed to it being self-pollinating, evolving from narrow wild germplasm and exhibiting very limited gene flow between wild and cultivated types. Backcrossing to introduce simply inherited desirable traits and utilization of improved breeding lines and varieties as parents in crossing programs further narrowed the genetic base of cowpea varieties. In most cowpea breeding programs, genes for resistance and market traits were pyramided into lines characterized by high levels of acceptance to farmers and consumers. Besides predisposing widely distributed improved varieties to genetic vulnerability, a narrow base of genetic variation may be contributing to the plateauing in cowpea grain yield, which compromises genetic gains. Cross compatible wild relatives have not been used in variety development because breeders shy away from them due to their tiny seed size, unattractive seed coat color and texture, pod shattering, and susceptibility to viruses. A number of wild cowpea relatives, both within and outside section Catiang of Vigna species, have been evaluated for their reaction to cowpea insect pests and diseases. Vigna vexillata lines were resistant to the legume pod borer (Maruca vitrata), the cowpea weevil (Callosobruchus maculatus), and Striga gesnerioides but are cross incompatible with cultivated cowpea. Some lines among the cross compatible wild relative V. unguiculata ssp. dekindtiana were found to be resistant to aphid in the seedling stage, while others showed good levels of drought and heat tolerance. Molecular markers are being generated to identify quantitative trait loci (QTL) with effects on some desirable attributes in cowpea. Modern breeding tools, including transgenics, can be applied for the improvement of cowpea, bypassing the natural barriers of traditional breeding. Transgenic cowpea with Bt gene cry1Ab showing resistance to M. vitrata has been released in Nigeria. Genome editing, a powerful emerging tool, can also be used for developing improved cowpea varieties with durable resistance to pests and diseases