Accessions Of African Yam Bean Research Articles

Comparative Study of Proximate, Mineral and Anti-nutrient Composition of African Yam Bean (Sphenostylis stenocarpa Hochst Ex. A. Rich. (Harms.) Accessions

Background: This study compared the proximate, mineral and anti-nutritional composition of selected accessions of African yam bean. The objective was to assess the potential of these accessions to contribute to food and nutrition security critical to the survival of many rural communities currently ravaged by hunger and malnutrition in Africa. Methods: Eight (8) accessions of African yam bean were used for this study. Seeds of each accession were processed and chemically analyzed using AOAC standard methods. The samples were replicated three times and F-LSD were used to separate significant means. Result: Results obtained showed that there were significant variations in the proximate, mineral and anti-nutritional composition of the accessions. Accession TSs 519 had the highest crude protein composition (22.53%), dry matter (91.14%), carbohydrate content (22.53%), sodium (80.46 mg/100 g) and the lowest moisture content 8.86%. The ash content was highest in accession TSs 568 (5.26%). Accession TSs 535 had the highest content of phytate (3.74%), oxalate (1.73%), HCN (1.72%) and tannins (1.44%). Magnesium and potassium were highest in accessions TSs 595 (90.26 mg/100 g) and TSs 568 (280.51 mg/100 g) respectively. The high protein and carbohydrate contents of African yam bean could supplement traditional dishes consumed by both children and adults in order to alleviate protein-energy malnutrition in the developing countries especially in Africa, where this legume is indigenous.

Evaluation of 93 Accessions of African Yam Bean (Sphenostylis stenocarpa) Grown in Ethiopia for Physical, Nutritional, Antinutritional, and Cooking Properties

African yam bean has immense food and nutrition potential and is resilient to adverse environmental conditions. Despite its potential, the crop is underutilized, which could be attributed to seed hardness (requiring about 6–24 hours of cooking time); and the abundance of antinutrient factors (tannin, phytate, and oxalate). This study evaluated the physical (seed hardness, cooking time) and chemical compositions (crude protein, tannin, phytate, and oxalate) of 93 AYB accessions grown in Ethiopia. The seed hardness of each accession was determined by the compression force and compression time using Texture Analyzer, whereas cooking time was ascertained using Mattson Bean Cooker. The accession’s crude protein level, tannin, oxalate, and phytate were investigated from flour samples using standard laboratory procedures. Highly significant ( P < 0.01 ) differences were observed for cluster means of compression force, cooking time, and oxalate. The accessions were grouped into three clusters: cluster-II was prominent with 42 accessions, while cluster-I had the least (25). The mean values for compression force ranged from 50.05 N ± 10.25 (TSs-423) to 278.05 N ± 13.42 (TSs-378) whereas compression time varied from 0.35 secs ± 0.02 (TSs-334) to 5.57 secs ± 6.12 (TSs-62B). Cooking time ranged from 127.50 mins ± 2.12 (TSs-82A) to 199.50 mins ± 10.61 (TSs-138B); crude protein ranged from 15.41% ± 0.11 (TSs-269) to 24.51% ± 0.22 (TSs-446). Tannin ranged from 0.61 mg/g ± 0.02 (TSs-47) to 9.62 mg/g ± 0.03 (TSs-334) likewise, phytate ranged from 0.28 ± 0.01 (TSs-137) to 7.01 ± 0.10 (TSs-3). Accessions TSs-55; TSs-82 showed the lowest oxalate content of 0.21% ± 0.01; 0.21% ± 0.00, respectively. Similarly, TSs-352; TSs-47 revealed the most abundant tannin content of 0.70 ± 0.00 and 0.70 ± 0.07. The correlation analysis revealed a low positive and significant ( P < 0.05 ) association (r = 0.24) between protein and phytate content.

Biochemical and Histopathological Studies of Key Tissues in Healthy Male Wistar Rats Fed on African Yam Bean Seed and Tuber Meals

Food insecurity and malnutrition are currently major issues affecting most developing countries, especially on the African continent. To mitigate this effect, focus is being given to orphan or underutilized crops with immense potentials to boost food and nutrition security in Africa, such as the African yam bean (AYB) Sphenostylis stenocarpa. The effect of AYB seed and tuber meals on the tissues of the kidney, liver, and testis of healthy male Wistar rats were investigated in this study. Four accessions of AYB were used for this study, TSs 107, TSs 140, AYB 45, and AYB 57. Thirty rats were randomly assigned into five groups (n = 6). Group I was fed on standard pelletized rat chow (control), Group II fed on 50% seed meal, Group III fed on 100% seed meal, Group IV fed on 50% tuber meal, and Group-V fed on 100% tuber meal. At the end of the treatments, the animals were sacrificed after 72 h under light ether anesthesia, and biochemical and histopathological analyses were conducted on the tissues. Phytate concentration was higher in the seeds (TSs140 (550 mg 100g−1), AYB45 (460 mg 100g−1), and AYB57 (485 mg 100g−1)) compared to the tubers (TSs140 (14.8 mg 100g−1), AYB 45 (275 mg 100g−1), and AYB57 (240 mg 100g−1)). The consumption of 100% unprocessed AYB seeds caused liver and kidney damage in rats due to increased levels of aspartate aminotransferase (5.04 ± 1.62 U L−I), alanine aminotransferase (8.46 ± 2.43 U L−I), and lipid peroxidation (0.27 ± 0.02-unit mg−1protein). AYB tubers were innocuous to Wistar rats investigated. Good processing of AYB seeds is required for safe consumption by humans and livestock. This study has shown that tubers of AYB are safe for human consumption and should be utilized in meals as it contains fewer antinutrients and had no significant effect on the tissues examined in Wistar rats.

Responses of African yam bean (<i>Sphenostylis stenocarpa</i> [Hochst. Ex A. Rich]) accessions to viral diseases and serological identification of the associated viruses

African yam bean (Sphenostylis stenocarpa) is an orphan crop with lofty nutraceutical benefits grown in Africa. However, pests and diseases often hinder its productivity. Twenty accessions of African yam bean (AYB) were screened for resistance to viral diseases and symptomatic leaves were indexed for the presence of viruses. The Field experiments were conducted during the 2015/2016 cropping seasons (wet and dry seasons). The twenty accessions were grown in triplicates in a randomized complete block design (RCBD) on the field under natural infection and the resistance or susceptibility responses were recorded using visual symptom expression. The characteristic symptoms that were highly prevalent were leaf mosaic and leaf distortion. In both seasons, there were significant (P< 0.05) differences in the severity of these viral symptoms. Also, based on the severity of the symptoms observed in this study, 2 accessions were classified as resistant, 16 as susceptible and 2 accessions as highly susceptible. Two viruses were identified serologically namely Cowpea Mild Mottle Virus (CPMMV) and Blackeye Cowpea Mosaic Virus (BlCMV). The sources of resistance identified in this study would be useful for breeders in developing virus resistant varieties for African yam bean improvement.
 Keywords: African yam bean, Virus, Symptoms, ACP-Elisa, Screening.

Evaluation of the Genetic Diversity of African Yam Bean (Sphenostylis stenocarpa (Hoechst. ex. A Rich.) Harms.) Using Seed Protein Marker

Aims: The present research seeks to assess the genetic diversity of African yam bean accessions in Nigeria using seed protein marker; geared towards its genetic improvement and conservation. Introduction: African yam bean is an “Orphan Crop” highly nutritious and has been listed to be among the underutilized legumes despite its immense nutritional advantages in human diets. African yam bean has been reported as a good source of essential amino acids including cysteine, lysine, methionine, phenylalanine and Proline.
 Study Design: Fifteen (15) accessions of African yam bean were collected from the International Institute for Tropical Agriculture (IITA), Ibadan and 25 local accessions were collected from different parts of Nigeria including Enugu.
 Results: This study evaluated the genetic diversity on forty (40) accessions of African yam bean (Sphenostylis stenocarpa) obtained from IITA germplasm bank and other parts of Nigeria. In this study, the genetic differences among the accessions were detected by the presence or absence of bands, which could be used as a basis for variation among accessions. The results from this present study revealed high polymorphism (≈93%), indicating high intra-specific genetic variation with potential linkage to traits desired by breeders.
 Conclusion: The study demonstrated that seed storage protein using SDS-PAGE is an important tool for genetic diversity study in African yam bean, providing baseline information. This baseline information will be useful in further molecular studies geared toward efficient breeding and conservation strategies for this crop.

Assessment of Seed and Tuber Production Potential in Varieties of <i>Sphenostylis stenocarpa</i> (Africa Yam Bean)

Twenty accessions of African Yam Bean, grown at the Teaching and Research Farm of Ladoke Akintola University of Technology, Ogbomoso during the cropping seasons of May to November, 2014 and 2015 were assessed for genetic diversity and Genotype × Environment interaction effects on trait performance and their ability to produce tuber. The first six Principal Components jointly explained 70.30% of the total variation among the accessions. Vine length, branching pattern, pod number, pod length, seed number, and seed yield contributed mostly to the observed variations. Seed biometric traits were most variable and contributed 52% of total variation. Variance due to genotype accounted for 54.2%, environment 10.5% and G × E interaction accounted for 30.1% of the interaction sum of squares. Accessions, G2, G4, G47, G49 and G50 produced tubers, while accessions G6, G15, G31, G32 and G33 nodulated extensively. Conversely, there was a marginal reduction in seed yield in accessions that either produced tubers or nodules.

Evaluation of the nutritional composition ofthe seeds of some selected African yam bean (<i>Sphenostylis stenocarpa</i> Hochst Ex. A. Rich (Harms)) accessions

African yam bean (AYB) is an important but neglected and underutilized crop producing edible seeds and tubers. The poor awareness of the nutritional values of AYB constitutes one of the major problems limiting its utilization. This study was, therefore, carried out to determine the nutritional potentials of five accessions of African yam bean (TSs 125, TSs 116, TSs 86, TSs 69 and TSs 60) by analyzing their proximate composition and micronutrients (Iron (Fe), Zinc (Zn) and Selenium (Se)). The experiment was laid out in completely randomized design (CRD) with three replications. The results obtained showed significant (p < 0.05) variations in the proximate composition of the AYB accession. The crude protein was in the range of 21.84-23.41 %, crude fat 3.40-3.86 %, fibre 6.17- 6.76 %, carbohydrate 52.8-54.48 %, dry matter 90.42 - 90.6 %, ash 4.22 - 4.35 %, and moisture 9.4 - 9.58 %.The Se concentration varied from 312 mg/100 g in TSs 116 to 58 mg/100 g in TSs 60 while Fe ranged between 10.40 mg/100g in TSs 60 and 6.07mg/100gin TSs 86. Zinc varied between 8.83 mg/100g in TSs116 and 6.37 mg/100 g in TSs 69.TSs 116 was best accession in terms of crude protein, dry matter, ash, selenium and zinc, while TSs 60 was best in terms of iron. The study revealed AYB seeds as a food crop rich in protein, carbohydrate, fibre, selenium, iron and zinc. The genotypic variability can be exploited in developing African yam bean varieties with better qualities in terms of nutrient density. Keywords: Neglected, underutilized, nutrient-dense, micronutrient and protein

Investigation of the Breeding Mechanism of African Yam Bean [Fabaceae] (Sphenostylis stenocarpa Hochst. Ex. A. Rich) Harms

The many reported inherent nutritional potential in African yam bean (Sphenostylis stenocarpa (Hochst. Ex. A. Rich.) Harms) seem to provide platform for the need of its genetic improvement. A good understanding of the breeding system of the crop species is a needed criterion in plant breeding program. Four accessions of African yam bean (AYB) collected from the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria were grown out in a fifteen plants/accession row on a field at IITA, Ibadan (7.5°N, 3.9°E), Nigeria. Five pollination mechanisms were investigated as treatments on the four accessions. The four accessions set fruits and seeds in four treatments: plants left to open-pollination (A), plants isolated with fine net mesh (B), artificially selfed flowers (C) and inter-varietal cross-pollination (D). Emasculated flowers which were not pollinated (treatment E) produced neither fruit nor seed. Treatment A differed significantly (P&lt;0.05) from B, likewise C and D. Fruit set percentage was higher in A (19.7-21.2) than B (18.3–18.7). Higher pollination/fertilization success (46.5%) was obtained in C compared to 32.3% in D. More seeds (88.6%) were set by self-pollination. The four accessions had a mean selfing rate of 89.8% and an outcrossing rate of 10.17%. The observed 1:9 allogamy: autogamy in this study could form the basis for developing the breeding strategy for the genetic improvement of AYB via hybridization.

Floral Maturation Indices of African Yam Bean (Sphenostylis stenocarpa Hochst Ex. A. Rich) Harms (Fabaceae)

The present investigation aimed at understanding the floral morphology and maturation indices of African yam bean (AYB), knowledge of which is very relevant for the crop’s improvement programs. Ten accessions of AYB were grown in rows of ten plants, in three replications. Thirty anthesized flowers were collected from each accession for the study of the floral parts. The progressive development of flowers from buds was additionally investigated. AYB flower is large and complete. The calyx was fused and the corolla has five petals (one standard, two wings and two keels). AYB accessions exhibited racemes and indeterminate form of inflorescence. The mean standard petal length and width were 2.94 cm and 3.59 cm respectively. The androecium which surrounded the carpel consists of ten filaments (nine fused, one free). The gynoecium comprised flattened stigma with hairy edge. The mean length of style and ovary was 1.60 cm and 1.00 cm respectively. A distinct purple line (along the enclosing end of the standard petals) became visible at flower bud stage, when bud length reached 2.2 cm - 2.7 cm. Anthesis occurred within 24 hours beyond this stage and petals dropped a day after anthesis. Certification of stigmatic receptivity and pollen fertility may be dependent on the above information. The present study further provides basis for the understanding of pollination mechanism and breeding system within the species.

Bivariate analysis of the genetic variability among some accessions of African Yam Bean (Sphenostylis stenocarpa (Hochst ex A. Rich)Harms)

Variability is an important factor to consider in crop improvement programmes. This study was conducted in two years to assess genetic variability and determine relationship between seed yield, its components and tuber production characters among twelve accessions of African yam bean. Data collected were subjected to combined analysis of variance (ANOVA), Principal Component Analysis (PCA), hierarchical and K-means clustering analyses. Results obtained revealed that genotype by year (G × Y) interaction had significant effects on some of variables measured (days to first flowering, days to 50 % flowering, number of pod per plant, pod length, seed yield and tuber yield per plant) in this study.The first five principal components (PC) with Eigen values greater than 1.0 accounted for about 66.70 % of the total variation, where PC1 and PC 2 accounted for 39.48 % of variation and were associated with seed and tuber yield variables. Three heterotic groups were clearly delineated among genotypes with accessions AY03 and AY10 identified for high seed yield and tuber yield respectively. Non-significant relationship that existed between tuber and seed yield per plant of these accessions was recommended for further test in various agro-ecologies for their suitability, adaptability and possible exploitation of heterosis to further improve the accessions.

GGE biplot application for adaptability of African yam bean grain yield to four agro-ecologies in Nigeria

Genotypes respond to environments differently; therefore it is important that their response to growing environment should be investigated in order to identify most suitable genotype(s) for specific environment. The objective of this study was to understand the adaptability of some accessions of African yam bean to different agro-ecologies of Nigeria. Thirty African yam bean (AYB) ( Sphenostylis stenocarpa (Hochst ex. A. Rich) Harms) accessions were evaluated for grain yield adaptability to four agro-environments in Nigeria. Genotype by environment (GE) interaction was significant (P < 0.01) for grain yield, with a range of 239.29 kg ha -1 (TSs 89) to 4130.46 kg ha -1 (TSs 33). Two principal component axes generated in the biplots explained 70.9% of the total variation due to the accessions and their interaction with the environments. The superior genotypes for each location were TSs82 (Ibadan), TSs116 (Mokwa), TSs24 (Ikenne) and TSs33 (Ubiaja). Three mega-environments arose from the study; namely Ikenne, Ubiaja and Mokwa (Ibadan merged with Mokwa to form a single megaenvironment). Ikenne was a more representative environment for AYB production, having a mean grain yield of 1074.53 kg ha -1 , closest to the grand mean of 1075.57 kg ha -1 . However, Ubiaja was most supportive for grain production of AYB. Some of the accessions identified with high yielding, adaptable/stable in the study included TSs101, TSs111, TSs93, TSs94, TSs57, TSs104B and TSs109. Key Words: Accessions, mega-environment, principal components, Sphenostylis stenocarpa

Fruit Morphometric and RAPD Evaluation of Intraspecific Variability in Some Accessions of African Yam Bean (Sphenostylis stenocarpa Hochst. ex. A. Rich. Harms)

African Yam Bean (AYB) (Sphenostylis stenocarpa, Hochst. ex A. Rich, Harms) is an indigenous underutilized legume mainly grown in Sub-saharan African as a source of protein. Intraspecific variability studies were carried out on 10 accessions of AYB obtained from the International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria. Fourteen (14) fruit morphometric characters and nine (9) arbitrary RAPD primers were employed for evaluation of genetic intra-specific variability among the accessions. A total of 410 bands were generated with 261 (63.66%) polymorphic bands. There is significant correlation among some reproductive characters; days to 50% flowering, pods per peduncle, number of locules per pod, number of seeds per pod, pod length and seed set percentage. These characters represent good markers of the taxon suitable for breeding and genetic improvement purposes. Morphometric and RAPD cluster analysis using UPGMA resulted in a dendrogram each; with membership similarity ranging from 72% to 93%. Two accessions (TSs56 and TSs94) recorded higher level of similarity index of 93% based on RAPD profiling. The morphometric evidences shows inherent stability of AYB across varied eco-geographical settings, which demands further investigation and exploitation. However, the RAPD evidences show that the species have evolved and adapted to distinct geographical setting with a clear Nigeria and Ghana demarcation. This fact can be engaged to guide future studies, germplasm collection, characterization, documentation, utilization and conservation of AYB to boost knowledge and awareness on the genetic diversity and utility of the species.

In vitro morphogenic responses of African yam bean (Sphenostylis stenocarpa (Hochst ex. A. Rich.) Harms) accessions to plant growth regulators

Morphogenic responses of two accessions of African yam bean to different concentrations of plant growth regulator supplements to Murashige and Skoog basal medium was investigated to develop a more efficient regeneration system. Mature embryo explants were cultured on growth regulator-free and BAP + NAA supplemented media. Nodal cuttings excised from 4-week old shoots of the regenerated embryos were cultured on media containing varying concentrations and combinations of 6-benzyl aminopurine (BAP), kinetin and α-naphthalene acetic acid (NAA). Growth regulator-free medium favored embryo regeneration and growth over supplemented media and both enhanced shoot regeneration and rooting, but could not induce multiple shoot formation on embryo explants. Multiple shoots were produced by nodal explants and the highest average number of shoots (5.3 ± 2.3), leaves (7.7 ± 3.6), roots (3.7 ± 2.9) and root length (3.1 ± 0.0 cm) were obtained on a medium with 0.6 mg l−1 BAP + 0.03 mg l−1 NAA for accession TSs154, while in TSs5, highest number of shoots (3.2 ± 2.5) and leaves (5.9 ± 1.5) were induced by 2.0 mg l−1 Kinetin + 0.05 mg l−1 NAA. Such differential morphogenic responses to culture media underline the genotypic control of in vitro propagation of this crop. Embryo and nodal explants rooted directly on shoot regeneration media, and regenerated plantlets were successfully acclimatized. The efficient regeneration system obtained will enhance genetic improvement of African yam bean by facilitating molecular genetic transformation for advanced breeding.

Physical, Proximate and Anti-nutritional Composition of African yam bean (Sphenostylis stenocarpa) Seeds Varieties

The physical, proximate and anti-nutritional properties of five accessions of African yam bean (AYB) seeds (TSs 57, TSs 61, TSs 93, TSs 94 and TSs 116) obtained from Genetic Resource Centre (GRC) of International Institute of Tropical Agriculture (IITA) were studied and compared. This was aimed at unraveling the nutritional importance of this crop to enhance its production and utilisation. The physical properties investigated include seed size, length to diameter ratio, seed weight, percentage of seed coat, bulk density and loose density. Proximate composition and anti-nutritional factors such as saponin, oxalate, phytate, alkaloids, tannin, trypsin inhibitor and hydrogen cyanide of these accessions processed flours were also examined. The results of physical properties indicated significant differences (P&amp;lt;0.05) among the accessions except accessions TSs 93 and TSs 94 that did not differ in their lengths and diameters and also accessions TSs 61 and TSs 116 did not differ in their thicknesses. Results of proximate analysis revealed that crude fibre, fat and carbohydrate contents of the accessions were not significantly different from one another at (P&amp;lt;0.05) except TSs 94 that differed in its carbohydrate and TSs 116 also differed in its crude fibre from others. Meanwhile, in terms of anti-nutritional factors, there existed no significant difference in saponin contents but there were significant differences in oxalate, phytate, alkaloids, tannin, trypsin inhibitor and hydrogen cyanide among the accessions tested.

Intraspecific variability in agro-morphological traits of African yam bean Sphenostylis stenocarpa (Hochst ex. A. Rich) harms

Intraspecific variabilities in 40 accessions of African yam bean (AYB) were assessed through characterization of 48 agromorphological traits for two cropping seasons between June and December 2011 and 2012. Data were analyzed using descriptive statistics, analysis of variance (ANOVA), correlation analysis, principal component analysis, and cluster analysis (Semi-partial R squared method). The accessions showed significant differences (P ≤ 0.05, P ≤ 0.01, P ≤ 0.0001) in 16 reproductive traits. Accessions TSs 66 (144.50 days), TSs 51 (144.67 days) and TSs 154 (144.67 days) were identified as early maturing accessions. The first five principal component axes explained 69.7% of the total variation with PC1 and PC2 contributing 38.9% to the total variation. Correlation coefficients were high and significant for yield traits. A highly significant correlation (r = 0.99***) was observed between seed yield (kg ha-1) and weight of total pods per plant. Tubers were produced from 42.5% of the accessions. The accessions of AYB were meaningfully grouped into five clusters at the R-squared distance of 0.04 similarity index. Phenotypically, AYB 57 and TSs 123 were the most similar accessions with the closest distance of 0.0071. Four seed shapes were identified; oval (82.5%), globular/round (5%), oblong (10%), and rhomboid (2.5%). In order to improve the yield of AYB, the number of seeds per pod, number of pods per plant, weight of total seeds per pod, and weight of total seed per plant are important determinant factors. The genetic variabilities observed in the traits studied could be utilised for improvement of AYB.

Genetic diversity in African yam bean accessions based on AFLP markers: towards a platform for germplasm improvement and utilization

Accurate knowledge of intra-specific diversity of underutilized crop species is a prerequisite for their genetic improvement and utilization. The diversity of 77 accessions of African yam bean (AYB, Sphenostylis stenocarpa) was assessed by amplified fragment length polymorphism (AFLP) markers. A total of EcoRI/MseI primer pairs were selected and 227 AFLP bands were generated, of which 59(26%) were found to be polymorphic in the 77 accessions of AYB. The most efficient primer combination for polymorphic detection was E-ACT/M-CAG with a polymorphic efficiency of 85.5%, while the least efficient was E-AGC/M-CAG with a polymorphic efficiency of 80.6%. The Jaccard genetic distance among the accessions of AYB ranged between 0.048 and 0.842 with a mean of 0.444. TSs98 and TSs104B were found to be the most similar accessions with a genetic similarity of 0.952. The neighbour-joining dendrogram grouped the 77 accessions of AYB into four distinct clusters comprising 8, 20, 21 and 28 accessions. The major clustering of the accessions was not related to their geographical origin. Cluster I was found to be the most diverse. The mean fixation index (0.203) and the mean expected heterozygosity (0.284) revealed a broad genetic base of the AYB accessions. The same germplasm set was previously evaluated for several agro-morphological traits. As the collection of additional AYB germplasm continues, the phenotypic profile, the clustering of the accessions and the AFLP primer combinations from this study can be used to augment breeding programmes.

English

The genetic diversity of 40 African yam bean (AYB) accessions was assessed using amplified fragment length polymorphism (AFLP) markers. Seeds of 40 accessions of AYB obtained from the International Institute of Tropical Agriculture (IITA) and Institute of Agricultural Research and Training (IAR&amp;T) Ibadan, Nigeria, were grown in a greenhouse and young leaves from two weeks old plants collected for DNA extraction. The four primer combinations used generated a total of 1730 amplification fragments across the AYB accessions used in this study of which 1647 were polymorphic (95.20%). The number of amplified polymorphic AFLP bands per primer pair varied from 360 to 520 with an average percentage polymorphism of 95.6%. E-AGC/M-CAG produced the highest number of polymorphic bands (520). Polymorphic information content (PIC) values ranged from 0.9447 to 0.9626. The highest level of polymorphism (100%) was recorded for two primer combinations (E-AAC/M-CAG and E-ACT/M-CAG). The results of cluster analysis using UPGMA tree, grouped the 40 accessions of AYB into two major clusters with an overall similarity of 67.5%. The level of similarity between the accessions spanned 0.66 to 0.91. TSs 138 and TSs 139 were the most closely related accessions with high level of similarity index (0.91). Comparable results were obtained using Factorial Coordinate Analysis (FCO).&nbsp; The results from the present study confirm the robustness and the suitability of the AFLP as a molecular tool for the assessment of genetic diversity in AYB accessions. &nbsp; Key words: Amplified fragment length polymorphism (AFLP), cluster analysis, genetic diversity, Sphenostylis stenocarpa, polymorphism.

English

Local accessions of African Yam Bean, a poorly studied and under-utilized but important food crop, from Abia, Akwa Ibom and Cross River states of Southern Nigeria were studied for variation in seed yield and pod characteristics. Correlations were carried out on the studied characters to determine the degree of mutual association among them while path coefficient analysis was used to partition the correlation coefficients into their direct and indirect effects on seed yield. Results revealed that significant differences (p&lt;0.01) exist among the accessions with respect to the studied characters. Mean number of seeds per pod ranged from 13.27 to 18.87; seed weight per pod from 3.19 to 6.21g; weight of 100 seeds from 22.86 to 36.72g; pod length from 21.67 to 36.82 cm and pod width ranged from 0.79 to 1.05 cm. Number of seeds per pod and pod length had significant positive association with seed weight per pod. Pod width also correlated positively with seed weight in some accessions. Positive direct effects on seed weight per pod were obtained with number of seeds per pod and pod length. The results taken together revealed significant variations in the accessions and provide evidence for effective selection which is a prerequisite for genetic improvement. &nbsp; Key words: Sphenostylis stenocarpa, accessions, variation, correlation, path coefficient analysis.

Evaluating the Effects of Staking and Planting Dates on the Yields of African Yam Bean, Sphenostylis stenocarpa in Nigeria

Aims: To evaluate the effects of staking and planting dates on the seed/tuber yields of African yam bean (AYB). Study Design: The fields were laid out in split-plots in randomized complete block design Place and Duration: Field experiments were conducted at Ebonyi State University, Abakaliki, Nigeria during 2009/10 farming seasons. Methodology: Three different planting dates were used as the main-plot treatments, while staking and non-staking formed the sub-plots. Seven accessions of AYB were planted in the sub-plots. Five plants were randomly selected from each accession/treatment and tagged for data collection. Each seedling was staked independent after germination, while the non-staked plants were allowed to trail on the ground guided. Collected data were subjected to analyses of variance. Mean separation was carried out by Fisher’s protected LSD test. Pearson correlation coefficient (r) was used to determine the relationship between yields, planting dates and staking. Results : The results indicated that all the AYB accessions performed better when they were staked and planted earlier in May of each season with greater seed/tuber yields, which differed significantly (P < 0.028) from those that were not staked and planted later in each of the season. Of all the accessions assessed, TSs86 was the most productive with the highest seed yield and differed significantly (P < 0.015) from the rest except TSs48 that even gave better seed yield during 2010, while TSs84 had the least seed yields. Results on

Reproductive mechanisms and pollen characterization in some accessions of an underutilized legume: (Sphenostylis stenocarpa Hochst Ex. A. Rich) harms

Studies on flowering, pollen, pod and seed characters, germination rate and seed set percentage were carried out on twenty five accessions of African Yam Bean (AYB). Self compatibility tests confirmed all the accessions as obligate selfers, while the reciprocal crosses were not successful. Germination rate, percentage seed set and pollen fertility were observed to be high in the accessions. Correlation analysis among the reproductive traits revealed that pod length, pod width, number of locules per pod and number of seeds per pod contributed significantly to the percentage seed set in all the accessions. Pollen fertility and seed viability were also observed to be high in all the accessions except in TSs23 where low pollen fertility, low seed viability and low percentage seed set were recorded. All the accessions produced tricolporate pollen grains. Pollen size ranged from 66.15 μm in TSs40 to 82.75 μm in TSs119, pollen fertility ranged from 53.39% in TSs23 to 95.30% in TSs119, seed set ranged from 83.32% in TSs90, 89.21% in TSs23 and 95.72% in TSs3. The germination rate ranged from 59.68% in TSs23 to 99.03% in TSs22. The percentage moisture content ranged between 4.38% in TSs22 and 11.43% in TSs119. Key words: Pollen characters, seed set, germination rate, self compatibility.