Centromeric banding pattern of mitotic chromosomes in Vigna vexillata (TVnu 73)

Vigna vexillata chromosome characterization was carried out using the Leishman C- banding technique. The results showed that the chromosomes mostly exhibited bands at both the centromeric and telomeric regions. These bands will serve, as a valuable marker for the identification of the chromosomes. Chromosomes 2 were the most variable and differed from the other chromosomes by the presence of satellite on the short arm. Diploid chromosome numbers of 22 consisting of 11 pairs of homologues were observed for V. vexillata. The homologues chromosomes were arranged in the descending order. The idiogram representing the chromosomes was also constructed.African Journal of Biotechnology Vol. 4 (5), pp. 400-402, 200

Characteristics of farmers’ selection criteria for cowpea (Vigna unguiculata) varieties differ between north and south regions of Burkina Faso

Open Access Article; Published online: 18 July 2019omparative analysis of preferences and key criteria for selecting cowpea (Vigna unguiculata L. Walp.) varieties was conducted using the data collected from farmers’ participatory varietal selection (FPVS) activities conducted over 3 years with a total of 2401 farmers (1230 male and 1171 female) in 13 villages in Tougouri department in northern region and Tiéfora department in southern region of Burkina Faso in West Africa. Over the 3 years, farmer criteria for variety selection remained basically stable, but some variations among the regions and years were noticed. Grain yield was the most common and the most important criterion for farmers’ choice in both regions. Farmers in Tougouri (north) put more emphasis on early maturity (90%) and drought resistance (19.7%) as selection criteria than farmers in Tiéfora (south). Farmers in Tiéfora placed statistically significant importance on seed colour and plant type, while farmers in Tougouri did not, and for these selection criteria, there were only slight differences between genders in both areas. Results of stepwise multiple regression indicated that maturity and seed colour in the north, and seed size and seed colour in the south were the most important selection factors for farmers to select cowpea varieties. Improved varieties should have sufficiently good yield to be accepted, but other favoured traits may differ by target region as a reflection of local and regional market demands as well as deep-rooted cultural preferences. Understanding local and regional differences in selection criteria for cowpea varieties is necessary to improve the acceptance of newly released improved varieties. Preferences identified in the participatory activities could inform further development of cowpea breeding strategies for north and south regions of Burkina Faso

A high plant density and the split application of chemical fertilizer increased the grain and protein content of cowpea (Vigna unguiculata) in Burkina Faso, west Africa

Open Access Journal; Published online: 31 Jan 2022In West Africa, cowpea (Vigna unguiculata) is an important source of protein for many people. To meet the protein demands, the cowpea yields per unit area and its seed protein content must be increased. We evaluated the effects of the planting density and topdressing (fertilisation) timing on the cowpea yield and its protein content. High density (HD: 40 × 40 cm) and super high density (SHD: 40 × 20 cm) plantings were the most efficient approaches for enhancing cowpea yields. Across different regions in Burkina Faso, under such approaches, the yield significantly increased by as much as 214.5%, with an average value of 88.9%. Fertilisation was not required to achieve the significant increases in cowpea production following dense planting. Although the yield increased, the seed weight per plant decreased with the increase in planting density. Applying topdressing when the plants started flowering increased the seed protein content significantly by up to 24.4%. Simple and robust technologies, such as high-density planting and topdressing, can be rapidly disseminated for increased cowpea yields and protein content improvement for Burkina Faso and for other countries

Genetic variability and trait association under thrips (Megalurothrips sjostedti Trybom) infestation in cowpea (Vigna unguiculata [L.] Walp.)

Open Access Article; Published online: 14 May 2021Flower bud thrips is one of the most destructive insect pests of cowpea in sub-Saharan Africa. Information on genetic variability among cowpea germplasm and interrelationships among traits under thrips infestation would facilitate the development of resistant varieties. The objectives of the study were to assess genetic variability for thrips resistance, estimate heritability of yield and other traits and investigate inter-trait relationships under thrips infestation. One hundred and fifty-six cowpea lines, including one resistant and one susceptible check, were screened for resistance under natural infestation at two locations in Nigeria, in 2016. Test lines were scored for thrips damage weekly for three consecutive weeks, after removal of spreader plants, to obtain damage scores (DS) 1, 2 and 3 while data were collected on agronomic traits. The data were subjected to analysis of variance from which genetic components of the phenotypic variance were computed. Interrelationships among traits were determined using phenotypic and genotypic correlation, and sequential path analyses. Significant variability was observed among test lines. Lines TVu 6824 and TVNu 1307 were identified as possessing thrips resistance. DS3 had significant genetic and phenotypic correlations with DS1, DS2 and yield-related traits. Number of pods per peduncle, number of peduncles per plant and DS3 were identified as first-order traits. Heritability estimates ranged from 0.55 to 0.73. Genetic variability among the lines suggests the possibility of genetic control of thrips while number of pods per peduncle, number of peduncles per plant and DS3 would serve as useful selection criteria for thrips resistance

Screening of Vigna unguiculata (L.) WALP. accessions from Togo for their reaction to Callosobruchus maculatus F.

Open Access Journal; Published online: 16 Mar 2022Post-harvest losses in cowpea are mostly caused by the infestation of Callosobruchus maculatus, a storage pest. It can cause up to 100% loss of untreated produce. Host Plant Resistance (HPR), an important component of integrated pest management, has potential for sustainable management of C. maculatus. The objective of this study was to assess a recently collected cowpea germplasm from Togo for resistance to C. maculatus. A total of 200 cowpea accessions from the five regions of Togo and five checks were screened for resistance to C. maculatus using a no-choice assay. The experiment was laid out in a completely randomized design (CRD) with three replications. Data were collected on average number of eggs laid (ANEL), average number of adult emergence (ANAE), number of holes per seed (NHPS), initial and final seed weight (ISW and FSW), median development period (MDP), percentage adult emergence (PAE), and percentage weight loss (PWL), and two indices of resistance computed viz. insect growth index (G.I.) and Dobie’s susceptibility index (DSI). Data collected were subjected to analysis of variance, Pearson’s correlation and stepwise multiple regression analysis. A total of 51 accessions were moderately resistant, among which RS009 and RP218 had the least DSI score. The remaining accessions (149) were susceptible. DSI was significantly correlated with ANAE, PWL and NHPS, and had a significant and negative correlation with MDP. The results of the stepwise multiple regression showed ANAE, PWL and MDP were the better predictors of cowpea bruchid resistance and accounted for 87.7% of the observed variation in DSI scores

Current status of molecular tools development for cowpea [Vigna unguiculata (L.) Walp.] improvement

Open Access ArticlesCowpea [Vigna unguiculata (L.) Walp.] is a popular tropical grain legume which is widely produced and consumed in sub-Saharan Africa (SSA). The grains are rich in dietary protein for human while the haulm is high quality fodder for livestock particularly ruminants. Compared with many other crops cowpea is a laggard in development, evaluation and deployment of different molecular markers for use in genetics and breeding. Application of DNA-based markers is of considerable significance to crop improvement. Some DNA based markers have been used to study genetic diversity, linkage and quantitative traits loci (QTL) mapping in cowpea. Results from these studies have demonstrated the extent of genetic diversity in cowpea and its relationship with other members of the Vigna species. In addition, genetic linkage maps have been produced and used for detection of QTLs for some desirable traits. Some of these include QTLs for seed size, seed coat and eye color, leaf shape, pod length, resistance to macrophomina, domestication-related traits such as pod length, days to flowering, etc. In view of the potential benefits of DNA markers to the development of better performing improved cowpea varieties, concerted efforts are now being devoted to develop molecular tools for the crop. The developed consensus genetic linkage map and genome sequence for cowpea will boost the application of molecular tools for its genetic improvement. A panel of 17 SNP markers have been developed for use in quality assurance and control in cowpea breeding activities. This review aims at highlighting the molecular approaches that have been used and being pursued for genetic diversity, QTL mapping of some qualitative and quantitative traits as well as marker-assisted selection leading to the development of high performing new improved lines that meet the needs of farmers and consumers

A genome-wide scan divulges key Loci involved in resistance to aphids (Aphis craccivora) in cowpea (Vigna unguiculata)

Open Access Journal; Published online: 01 Nov 2022Cowpea aphids (Aphis craccivora Koch) double as a direct damaging pest and a virus vector to cowpea, threatening the economic yield of the crop. Given the multiple ecotypes, different alleles have been implicated in aphid resistance, necessitating the identification of key genes involved. The present study implemented a genome-wide scan using 365 cowpea mini-core accessions to decipher loci involved in resistance to aphid ecotype from Kano, Nigeria. Accessions were artificially inoculated with A. craccivora in insect-proof cages and damage severity assessed at 21 days after infestation. Significant phenotypic differences based on aphid damage severity were registered among the accessions. Skewed phenotypic distributions were depicted in the population, suggesting the involvement of major genes in the control of resistance. A genome-wide scan identified three major regions on chromosomes Vu10, Vu08 and Vu02, and two minor ones on chromosomes Vu01 and Vu06, that were significantly associated with aphid resistance. These regions harbored several genes, out of which, five viz Vigun01g233100.1, Vigun02g088900.1, Vigun06g224900.1, Vigun08g030200.1 and Vigun10g031100.1 were the most proximal to the peak single nucleotide polymorphisms (SNPs) positions. These genes are expressed under stress signaling, mechanical wounding and insect feeding. The uncovered loci contribute towards establishing a marker-assisted breeding platform and building durable resistance against aphids in cowpea

Evaluation of cowpea mini core accessions for resistance to flower bud thrips Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae)

Open Access ArticleThe flower bud thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae), is an economically important pest of cowpea in sub‐Saharan Africa. Varietal resistance is the most preferred, environmentally friendly, cost‐effective and sustainable option for controlling this pest. The objective of this study was to identify sources of resistance to M. sjostedti among mini core accessions from the largest world cowpea germplasm collection maintained at the International Institute of Tropical Agriculture (IITA). The study was conducted during the 2015 and 2016 cropping seasons where 365 accessions were screened under field conditions. Each accession was rated visually for thrips damage score, flower abortion rate, number of pods per plant and number of thrips per flower. The resistance levels observed in genotypes TVu8631, TVu16368, TVu8671 and TVu7325 were similar to that of the resistant check “Sanzisabinli” (called Sanzi) during both seasons. In addition, 56 mini core genotypes showed moderate resistance to thrips damage. High heritability values were associated with thrips damage scores at 65 days after planting (0.60), percentage of effective peduncles (0.59), flower bud abortion rate (0.59), number of pods per plant (0.51) and number of peduncles with pods (0.5). The accessions identified with good levels of resistance to flower bud thrips will be used in cowpea breeding programs to develop improved resistant varieties

Inheritance of pod length and other yield components in two cowpea and yard-long bean crosses

Open Access Article; Published online: 2 Apr 2021This study determined the gene effects involved in the inheritance of pod length and other yield-related traits and relationships among traits in crosses between two cowpea lines (TVu 2280 and TVu 2027) and a yard-long bean (TVu 6642) line with long pods. Plants of six generations (P1, P2, F1, F2, BC1P1, and BC1P2) derived from TVu 2280 × TVu 6642 and TVu 2027 × TVu 6642 were evaluated under field conditions. Data collected on 14 yield components of each cross were used for generation mean analysis. Gene effects and their magnitudes varied with the crosses; digenic epistatic gene effects were detected for 10 traits in TVu 2280 × TVu 6642 and 11 traits in TVu 2280 × TVu 6642. Only additive gene effect was significant for pod length in TVu 2280 × TVu 6642 while additive, dominant, and two of the three digenic epistatic gene effects were significant in TVu 2027 × TVu 6642. Models that incorporated only significant additive, dominant, and digenic epistasis were adequate for all 14 traits in TVu 2280 × TVu 6642 and eight of the 12 traits in TVu 2027 × TVu 6642 for which model-fitting was possible. Across segregating generation of the two crosses, pod length (PodLNT) was significantly (p < 0.001) correlated with three major yield components viz. pod weight (0.84, 0.77), number of seeds per pod (0.41, 0.30) and seed weight per pod (0.61, 0.29). Significant correlation of PodLNT with seed yield per plant was moderate and significant (p < 0.01–0.001) in the BC1P1 of the two crosses (0.31 and 0.41). An improvement in cowpea seed yield is feasible through selection for long pods in segregating generations involving crosses with yard-long bean

Evaluation of cowpea accessions for resistance to flower bud thrips (Megalurothrips sjostedti) in Mali

Open Access JournalFlower bud thrips (Megalurothrips sjostedti) is one of the most damaging pests to cowpea in Africa and varietal resistance is one of the effective approaches to minimize the pest damage. Study was conducted to assess variability among 117 genotypes in addition to two resistant (Sanzisabinli and TVu 1509) and one susceptible (Vita7) checks at Cinzana and N’Tarla locations under natural and artificial infestations of thrips. Parameters such as total number of pods per plant and damage scoring were used to assess the test entries. Genotypes CIPEA82672, Suivita2, TVu 1509 and Sanzisabinli were found highly tolerant, Diaye and TVu7677 moderately tolerant whilst nine genotypes were found tolerant to thrips attacks. CIPEA82672 and Suivita2 had higher grain yield than the resistant checks. Year by genotype, year by location and year by location by genotype interactions were significant for most traits. Genotype by genotype by environment (GGE) effect on yield showed CIPEA82672 most stable across both locations while Suivita2 was only stable at N’Tarla. High broad sense heritability (H2b) was observed for some traits such as damage scoring across locations. Highest genotypic coefficient of variation (GCV) of 81.24 and phenotypic coefficient of variation (PCV) of 75.62 were attributed to total number of pods per plant. Positive correlations were detected between the damage scoring and the number of adult thrips from Cinzana (R2= 0.264) and N’Tarla (R2= 0.603) locations. Confirmation of identified cowpea genotypes highly and moderately tolerant to thrips attacks could be used to improve farmers’ preferred cowpea genotypes susceptible to thrips