Resistant Cowpea Research Articles

IMPACT OF PESTICIDE TOLERANT SOIL BACTERIA ON DISEASE CONTROL, PLANT GROWTH PROMOTION AND SYSTEMIC RESISTANCE IN COWPEA

Cowpea, an annual legume, suffers from several disease symptoms caused by Macrophomina phaseolina. Rhizobacteria isolated from pesticide infested soil, identified by blast analysis as Bacillus cereus, Bacillus safensis, Pseudomonas donghuensis and Pseudomonas aeruginosa ascertained tolerant to at least 0.1% pesticides viz. methomyl, imidacloprid and carbendazim. In vitro antagonism against pathogen exhibited maximum by P. aeruginosa 63%. All rhizobacteria were bestowed with attributes responsible for pathogen control and plant growth promotion. Field evaluation resulted highest 75% disease control, enhancement of length, nodule counts, biomass or yield per plant by P. aeruginosa. All rhizobacteria induced systemic resistance in cowpea under challenged inoculation with pathogen by augmenting defensive enzyme production. Highest Phenylalanine Ammonia Lyase activity was expressed in P. aeruginosa treated plants 1.02 μMoles/ml/min, Polyphenol Oxidase by P. donghuensis 1.39 μMoles/ml/min, Chitinase by B. cereus 0.745 μMoles/ml/min and 400 percent relative activity of Peroxidase by P. aeruginosa. The rhizobacteria were prospective for plant disease control, growth promotion and as immunity boosters in pesticide and heavy metal infested toxic environment.

Cowpea resistance and bioactivity of two diatomaceous earths against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) on three cowpea varieties

The bruchid, Callosobruchus maculatus (F.) is the most important pest of stored cowpea in tropical climates. Experiments were conducted to evaluate the susceptibility of three cowpea varieties and the bioactivity of SilicoSec® and FossilShield® against this insect pest under ambient laboratory conditions at the contents 0, 0.5, 1, 1.5 and 2 g/kg of cowpea. The Dobie susceptibility index for cowpea genotypes was estimated to compare their relative tolerance to this insect pest. Adult mortality was assessed after 1, 2, 4 and 6 days of exposure followed by the evaluation of the F1 progeny. Population increase, percentage seed damage and weight loss were assessed after three months of storage. The results showed that the CRPS and TN5-78 varieties were highly susceptible to C. maculatus, while Lori variety was moderately susceptible to the weevil. SilicoSec® and FossilShield® caused a significant and increasing bruchid mortality according to the dose rates and periods of exposure. Malathion 5% caused complete mortality after one day exposure time. SilicoSec® was more effective than FossilShield® on the three varieties of cowpea. The greatest dose of SilicoSec® and FossilShield® (2 g/kg) caused 100% mortality on all three varieties; 4 days of exposure in the Lori variety was the shortest exposure time leading to complete mortality. Regarding LD50 and LD95 values, it was observed that C. maculatus adults are more susceptible to SilicoSec® than to FossilShield®.The two formulations of diatomaceous earth (1.5 g/kg) reduced the F1 progeny by more than 70%, and produced less than 10% of seed damage and weight loss for the three varieties of cowpea. The varietal resistance and the use of diatomaceous earth against C. maculatus in storage could represent an alternative to Malagrain® for the protection of the cowpea.

Determination of inheritance of aphid resistance in cowpea genotypes and identification of single sequence repeat markers linked to resistance genes

AbstractAn understanding of the mode of inheritance is fundamental to plant breeding. The choice of an appropriate selection method considers the number of genes involved and their modes of action. In plant breeding, markers can overcome the false resistance that may arise from greenhouse screening. The goal of this study was to facilitate the better use of cowpea genotypes resistant to aphids. Specifically, we sought to determine the number of genes involved in the ability of cowpeas to survive aphid infestation and identify single sequence repeat (SSR) markers linked to aphid resistance genes. Two pairs of parents (Tiligre × KVX295‐124‐2‐99 and Tiligre × IT97K556‐6) were used to generate two F2 populations. Each of these populations was screened with aphids to determine the mode of inheritance of resistance to aphids in cowpeas. SSR markers were used to screen parent, F1, and F2 individuals to locate polymorphic markers and markers linked to the genes involved in resistance to aphids. The results showed that the ability to survive under aphid infestation in KVX295‐2‐124‐99 and IT97K556‐6 is controlled by two nonallelic genes. The markers MA61 and MA70 were found linked to aphid resistance in cowpea.

Manjari: A Cowpea Aphid Borne Mosaic Virus (CABMV) tolerant yard long bean (Vigna unguiculata ssp. sesquipedalis (L) Verdc) variety suited for problem zone of Kerala

Cowpea is an important vegetable crop worldwide and it contributes to nutritional security, income generation and soil fertility enhancement. The production of cowpea is limited by several biotic and abiotic stresses. Among the biotic stresses, cowpea aphid-borne mosaic virus (CABMV) is a major virus disease that results in substantial yield loss to the crop. The development and release of resistant varieties is the most viable option in the management of this disease. The objective of the study was to develop CABMV resistant cowpea varieties without compromising yield and quality which are suited for intercropping as well as pure crops. Backcross breeding for imparting disease resistance was performed in which CABMV resistance was transferred from the cultivar CO6. KMV1 is a superior variety suited for intercropping in coconut gardens and well suited to the special problem zone of Kerala but susceptible to virus disease. The segregating generations up to BC4F3 were evaluated for disease resistance and economically important traits. The economically superior selection having CABMV resistance was released as variety Manjari. The variety possesses the characteristics of tolerance to mosaic disease, shade tolerance, ideal for intercropping and very good culinary characters. Key words: Yard long bean, CABMV resistance, Vigna ungiculata ssp. Sesquipedalis

Morpho-agronomy performance, seed nutrition content, and Aphis craccivora resistance of cowpea (Vigna unguiculata) genotypes

Abstract. Sas MGA, Wahyu Y, Syukur M, Hidayat P. 2021. Morpho-agronomy performance, seed nutrition content, and Aphis craccivora resistance of cowpea (Vigna unguiculata) genotypes. Biodiversitas 22: 4320-4326. Cowpea (Vigna unguiculata subsp. unguiculata) is an agricultural commodity that can be a source of vegetable protein and replace the need for soy as a food ingredient. The wide adaptability under sub-optimum conditions placed cowpeas as the choice to be developed. This study aimed to evaluate the cowpea genotype’s agronomic performance and resistance to Aphis craccivora to be proposed as superior genotypes. Observations were made on the morpho-agronomic characters, including the color of the young pods and dry seeds, the number of pods, the productivity of fresh pods and dried seeds, and the nutrition content. The resistance to Aphis craccivora was evaluated using a no-choice test whole plant for the resistance and tolerance evaluation. This study showed that the productivity of young pods (4.86-15.13 tons ha-1), dry seed productivity (0.83-2.71 tons ha-1). The protein content differed significantly among the 20 genotypes ranging from 19.24% to 24.45%. Aphid infestation significantly inhibited plant growth compared with non-infested plants. Infestation of Aphis craccivora decreased the dry weight of the plant by about 20% to 70%. Based on the aphid population, the 20 genotypes were classified into medium-high to very high aphid damage intensity.

English

Brown blotch disease caused by Colletotrichum capsici, is one of the most important disease affecting cowpea production in Burkna Faso. Every year the disease can cause yield losses as high as 42 to 100% on farmer’s fileds. This study aimed to understand the inheritance of its resistance in cowpea and also identify quantitative trait loci (QTL) associated with the resistance. Seedlings of parents and F1, F2 and BC1F1 progenies from crosses involving four susceptible and four resistant parents were screened in greenhouse conditions for brown blotch disease reaction. The inheritance studies indicated that different genes action were involved in the resistance of brown blotch resistance disease. In KN-1 variety, two or several genes associated to brown blotch were suggested. In Donsin local, a partially dominant gene, Rcc1, would be associated with the resistance. In Moussa local, a single major dominant gene, Rcc2, was identified. A single major recessive gene, rcc2, was found to control resistance with brown blotch in the cowpea resistant variety IT93K-503/46-13. The research of gene or QTL associated with brown blotch in cowpea variety KN-1 has been investigated. Polymorphic single nucleotide polymorphisms (SNP) markers and QTL associated to brown blotch resistance were discovered from 63 F2 individuals from a cross involving the susceptible variety Tiligre and the resistant KN-1. More than 11800 polymorphic SNP markers covered 1019.3 cM of the whole genome of cowpea were identified. A single dominant QTL, nomed qBBDR2 and 102 individual SNP markers tightly associated with the resistance of C. capsici were identified on chromosome 2 (Phytozome) of the cowpea genome. Key word: Cowpea, Colletotrichum capsici, resistance, inheritance, single nucleotide polymorphisms (SNP) marker, QTL.

Biological and Molecular Evidence for the Existence of Bruchid Ecotypes in the Nigerian Cowpea Ecosystem

The oviposition, growth and development of six populations of Callosobruchus maculatus (IT, PH, UM, MD‐1, MD‐2, MD‐3) from different localities in Nigeria were studied on a resistant (TVu 2027) and susceptible (Ife Brown) cowpea cultivar and four cultivars of African yam bean, Progenies obtained by cross‐mating individuals from the different populations were also studied.. Oviposition was highest in the MD insect beetle population and lowest in the UM population. IT and PH populations had the highest adult emergence and shortest development times on the resistant control. Genomic differences among bruchid populations were confirmed by the Random Amplified Polymorphic DNA (RAPD) fingerprinting technique with PH population being the most distant. All progenies with IT as the female parent also had better emergence and shorter development time than their reciprocal crosses or those involving other populations, but this varied with the fitness of the male parent. The UM population averaged <10% adult emergence on TVu 2027 compared to 71.9 % on the susceptible control, but was better adapted to the AYB (66 % emergence) than were other populations. These results suggest possible existence of ecotypes, of this bruchid species in Nigeria with potentially important implications for the development and deployment of resistant cowpea varieties.

Primary and secondary metabolite compounds in cowpea seeds resistant to the cowpea bruchid [Callosobruchus maculatus (F.)] in postharvest storage

Cowpea is a one important legume crop in Sub-Saharan Africa due to its high content of protein and other nutrients. However, seeds of cowpea varieties are destroyed by Callosobruchus maculatus in storage. This study investigated various biochemical compounds of susceptible and resistant cowpea genotypes, to determine the biochemical compounds underlying cowpea resistance to bruchid. Six cowpea genotypes were analyzed in three replicates. One-way analysis of variance, Pearson correlation and path analysis were used to determine the influence of the biochemical compounds on the cowpea status. Amongst the cowpea genotypes assayed the biochemical compounds analyzed (Vicilin; α-amylase Inhibitor; Phenols; Condensed Tannin; Tannin; Carbohydrate; Flavonoid and Protein), were present in amounts. Resistant genotypes exhibited higher contents of Phenols (22.29 mg/g for WC66*5T and 19.74 mg/g for WC36); Tannin (2.45CEmg/g for WC36 and 2.52CEmg/g for TVU13677); and Carbohydrate (72.82% for TVU13677 and 71.09% for WC36). The most susceptible genotypes had the lowest content of Phenols (13.5 mg/g for TVU946 and 12.72 mg/g for Glessissaffodo); Tannin (0.74CEmg/g for Akounado and 0.97CEmg/g for Glessissaffodo) and Carbohydrate (60.95% for Akounado and 61.39% for TVU946), while Condensed Tannin was associated to their seed coat colour but not to their resistance status against bruchid. The resistant genotypes TVU13677; WC36 and WC66*5T were found to contain a higher amount of a subset of biochemical compounds as defensive compounds against cowpea bruchid. The susceptible cowpea genotypes (Akounado; Glessissaffodo; TVU946) screened for their biochemical content presented low amounts of these defensive compounds. The path analysis implemented highlighted the existence of causal relationships among biochemical compounds analyzed and resistance parameters, thus revealing the resistance basis of cowpea seed biochemical compounds. These latter results point out the possibilities to consider the presence of these biochemical compounds underlying the resistance of cowpea to bruchid in the breeding program toward the resistance to bruchid.

Disparate genetic variants associated with distinct components of cowpea resistance to the seed beetle Callosobruchus maculatus.

Polygenic genome-wide association mapping identified two regions of the cowpea genome associated with different components of resistance to its major post-harvest pest, the seed beetle Callosobruchus maculatus. Cowpea (Vigna unguiculata) is an important grain and fodder crop in arid and semi-arid regions of Africa, Asia, and South America, where the cowpea seed beetle, Callosobruchus maculatus, is a serious post-harvest pest. Development of cultivars resistant to C. maculatus population growth in storage could increase grain yield and quality and reduce reliance on insecticides. Here, we use a MAGIC (multi-parent, advanced-generation intercross) population of cowpea consisting of 305 recombinant inbred lines (RILs) to identify genetic variants associated with resistance to seed beetles. Because inferences regarding the genetic basis of resistance may depend on the source of the pest or the assay protocol, we used two divergent geographic populations of C. maculatus and two complementary assays to measure several aspects of resistance. Using polygenic genome-wide association mapping models, we found that the cowpea RILs harbor substantial additive-genetic variation for most resistance measures. Variation in several components of resistance, including larval development time and survival, was largely explained by one or several linked loci on chromosome 5. A second region on chromosome 8 explained increased seed resistance via the induction of early-exiting larvae. Neither of these regions contained genes previously associated with resistance to insects that infest grain legumes. We found some evidence of gene-gene interactions affecting resistance, but epistasis did not contribute substantially to resistance variation in this mapping population. The combination of mostly high heritabilities and a relatively consistent and simple genetic architecture increases the feasibility of breeding for enhanced resistance to C. maculatus.

Efforts in breeding cowpea for aphid resistance: a review

ABSTRACT Cowpea is an important food and nutritional security grain legume crop in the semi-arid regions of sub-Saharan Africa. Its production is limited by biotic factors including pre-harvest insect pests such as aphids. Aphids cause yield reductions, promotes the growth of sooty moulds, honeydew and as a result reduce photosynthetic processes and rates. Various methods have been deployed to try to control the damage of aphids in cowpea plants. The methods include the use of chemical insecticides, cultural, mechanical, biological controls and integrated pest management. However, these methods have not been very effective as smallholder farmers growing cowpea in marginal areas cannot afford them. Hence, host plant resistance/genetic control is the best and effective method for controlling aphids in cowpea plantations. Breeding for aphid resistance is one of the effective methods that can sustain the production and productivity of the cowpea for longer periods. Furthermore, assessing the presence of genetic diversity can also help in sourcing genes of novelty for addressing this important issue to increase the production and productivity of the crop. Recently, scientists have used various strategies to try to solve the challenge of aphid damage on cowpea. The objective of this review was to document the research progresses on aphid resistance breeding of cowpea to facilitate the breeding and conservation of cowpea germplasm. The review serves as a baseline information to guide future cowpea breeding for resistance to aphids.

Distribution and diversity of alternate hosts of Maruca vitrata\xa0Fabricius in three West African countries

The evolution of resistance to the Bacillus thuringiensis (Bt) toxins by insect pests is a major threat to Bt technology. However, the rate of resistance can be slowed with appropriate integrated insect resistance management (IRM) strategies. Surveys were conducted to identify alternate host species for Maruca vitrata (commonly called the legume pod borer or Maruca) that could serve as refuges for Pod-Borer Resistant (PBR) cowpea in three West African countries (Ghana, Nigeria, and Burkina Faso). Survey sites included 25 in northern Ghana, 44 in northern Nigeria, and 52 in north-central and southwestern Burkina Faso. Alternate hosts of Maruca identified from plant species belonging to the Fabaceae family that showed signs of Maruca damage on cowpea tissues were collected and dissected. Larvae that were found during these dissections were reared to adult moths in the laboratory then identified to species. The alternate host plants including species of Crotolaria, Sesbania, Tephrosia, and Vigna were the most frequently encountered among sites and locations. Flowering and podding of these plants overlapped with flowering and podding of the nearby (~200 m) cowpea crop. Abundance of these wild hosts and overlapping flowering patterns with the cowpea crop in most locations have the potential to sustain ample numbers of Bt susceptible Maruca that will mate with possible resistant Maruca and deter resistance development. Further quantitative studies, however, are required from each location to determine if actual Maruca production from alternate hosts is sufficient for a PBR IRM strategy. If verified, this approach would be compatible with the high dose/refuge IRM strategy that includes alternate hosts and non-Bt crops as refuges.

Resistance to Meloidogyne enterolobii and Meloidogyne incognita in Cultivated and Wild Cowpea

Cowpea [Vigna unguiculata (L.) Walp] is a multipurpose crop that provides nutrients for human and livestock diets, as well as regulates and supports ecosystem services. In developing countries, cowpea is exploited as a dual-purpose crop for its grain and fodder; it is cultivated primarily for grain and as a cover crop in industrialized countries. However, root-knot nematodes (RKNs) (Meloidogyne spp.) represent a threat to cowpea production worldwide. Thus, we screened the University of California, Riverside (UC-Riverside), cowpea mini-core collection for resistance to Meloidogyne incognita Kofoid and White (Chitwood) and M. enterolobii Yang and Eisenback to verify the potential of this collection to be used for improving RKN resistance in cowpeas. Both screenings showed significant genotypic variation and medium/high broad-sense heritability (H2) estimates for most traits, and several traits were also strongly correlated. For the M. incognita screening, 86.1% of accessions showed some level of resistance based on gall score (≤3), and 77.7% based on reproduction index (RI) (25 ≤ RI ≤ 50), whereas only 10.4% and 29.8% of accessions were resistant to M. enterolobii based on gall score (≤3) and RI (25 ≤ RI ≤ 50), respectively. These results demonstrate the greater virulence of M. enterolobii than M. incognita in cowpea, and that geographic origin of germplasm was not linked to sources of resistance. Among cultivars, only US-1136 showed resistance against both nematode species, whereas 12 wild/landrace germplasms exhibited resistance to M. incognita and M. enterolobii, and can be exploited for breeding resistant cowpeas.

Inheritance of genetic resistance to fusarium wilt in cowpea

Information on the inheritance of cowpea resistance to Fusarium oxysporum f. sp. tracheiphilum infections are relatively unknown. The goal of the present work was to determine the inheritance of cowpea resistance (denoted by MNCO1-649F-2-1 genotype) to Fusarium wilt and to recommend the best method to incorporate this resistance in susceptible genotypes. Two parent genotypes MNCO1-649F-2-1 (resistant) and cultivar BR-17 Gurgueia (susceptible) were crossed in a greenhouse. The hybridization between susceptible and resistant parents was performed to obtain F1 plants, which were crossed among themselves to obtain F2 plants. All plants presenting the first pair of developed leaves were inoculated with a conidial suspension of F. oxysporum f. sp. tracheiphilum (106 conidia/mL) by conidia root-immersion methodology. The assessment of fusarium wilt intensity was performed at 21 days after inoculation, with the aid of a descriptive scale. According to chi-square (χ2) test, the segregating ratios of 1:0 (resistant:susceptible) was accepted for F1 generation, and the ratio of 3:1 (resistant:susceptible) was accepted in F2 generation, assuming a dominant monogenic character, supported with results in the backcrosses. Maximum-likelihood methods confirm that resistance is attributed only to genes with major effects, and the analysis with means values and variance of populations also presented a monogenic inheritance. Our results make it possible to recommend backcrossing to introduce resistance in susceptible genotypes.

Identification of Resistant Cowpea (Vigna unguiculata (L.) Walp.) Genotypes against Charcoal under Artificial Inoculation

Identification of Resistant Cowpea (Vigna unguiculata (L.) Walp.) Genotypes against Charcoal under Artificial Inoculation

Rotations with Crotalaria spp. do not suppress populations of Meloidogyne incognita in cotton

Summary Field studies were conducted in Mato Grosso, Brazil and Georgia, USA to evaluate the efficacy of Crotalaria spp. as a rotational cover crop for managing Meloidogyne incognita in cotton (Gossypium hirsutum). The two studies differed in how Crotalaria spp. were incorporated into the cotton production system to reflect differences in climate (tropical vs subtropical) and production systems typical for the two regions. In Mato Grosso, Crotalaria juncea and C. spectabilis were planted after soybean in late summer, grown for approximately 300 days, and incorporated into the soil 6-15 days prior to cotton planting. In Georgia, C. juncea and a nematode-resistant cowpea, Vigna ungiculata, were planted after maize in the late summer, grown until killed by frost in the early winter, and cotton was planted in the next season. Soil population densities of M. incognita and root galling in cotton were similar in cotton following either fallow, resistant cowpea, or Crotalaria spp. However, Crotalaria spp. significantly increased cotton plant height at the time of harvest relative to the other treatments. Except for one of the experiments in Brazil, incorporation of Crotalaria spp. in the rotational scheme did not increase cotton yield. Results indicate that a cover crop of Crotalaria spp. does not suppress M. incognita in cotton production system more than a fallow period or planting a resistant cover crop.

Inheritance and combining ability estimates for cowpea resistance to bruchid (Callosobruchus maculatus Fab.) in Benin cowpea

Cowpea bruchid (Callosobruchus maculatus Fab.) is the most important storage pest causing significant economic losses. Development of bruchid resistant cowpea varieties is the most sustainable strategy for controlling bruchid. However, information regarding the nature of gene action governing the resistance to bruchid is limited for cowpea genotypes in Benin. This study aimed to understand the genetic basis of cowpea resistance to C. maculatus. Eight parents were crossed in a full diallel mating design. 56 F2 progenies were tested with the eight parental genotypes in alpha lattice design with three replications in laboratory. Data were recorded on bruchid emergence (BE); weight loss (WL); median development period (MDP); Dobie susceptibility index (DSI); number of eggs laid (NEL); average number of holes (ANH); seed damage (SD). Combining ability analysis was performed using Griffin's method 1, model 1 in AGD-R software. The results showed that general combining ability (GCA) effects were highly significant (p < 0.001) and negative for BE, WL, DSI, NEL, ANH, and SD on the parents. Significant positive GCA effects were observed for MDP. Thus, the parents TVU13677, IT84S2246-4, WC36 and WC66*5T were the best combiners for bruchid resistant. High narrow sense heritability was observed for BE (0.75), WL (0.69), DSI (0.72), ANH (0.77) and SD (0.69). These results showed that both additive and non-additive gene action govern the resistance to bruchid in cowpea. The genotypes (TVU13677; IT84S2246-4; WC36; WC66*5T) and the resistant crosses were the promising genotypes and can be used in breeding programs seeking to develop bruchid resistant cowpea varieties. • Cowpea is a major source of dietary protein in Sub-Saharan Africa. • Bruchid is the most important storage cowpea pest causing significant losses. • This study evaluated the Inheritance of C. maculatus resistance in cowpea. • The hopeful cowpea genotypes useable in breeding programs were found.

The resistance of the cowpea cv. BRS Xiquexique to infestation by cowpea weevil is related to the presence of toxic chitin-binding proteins

The cowpea weevil (Callosobruchus maculatus) is the main pest that attacks cowpea (Vigna unguiculata) seeds during storage, causing nutritional and economic losses in the cowpea crop. Thus, studies aiming to identify resistant cowpea cultivars have been developed. Chitin-binding proteins (CBP), such vicilins and chitinases, have been detected in seeds and related with the toxicity to insects. In this work, we investigated the presence of chitin-binding proteins in the partially resistant cowpea cv. BRS Xiquexique and evaluated their toxicity towards cowpea weevil. The CBP fraction was isolated by chitin affinity chromatography. CBP fraction showed, through 15% SDS PAGE, protein bands with varying molecular masses, mainly below 55 kDa. Proteins present in CBP fraction were identified by Western blotting and mass spectrometry analysis, as vicilins and chitinases. CBP fraction, at 5%, was able to interfere with the development of cowpea weevil, decreasing larval mass and length. A CBV (chitin-binding vicilin) fraction isolated from CBP fraction was toxic, at 2.0%, to C. maculatus, decreasing larval mass and length in 64.3% and 33.23%, respectively. These results suggest that chitin binding proteins, such vicilins and chitinases, may be related to the resistance of cowpea cv. BRS Xiquexique to the infestation by C. maculatus.

Conventional breeding of insect-resistant crop plants: still the best way to feed the world population.

Insect-resistant crops feed much of the world, using reduced carbon inputs and providing much greater economic returns on investment. Newer, more efficient efforts are urgently needed to speed development of insect-resistant plants before a projected 30% global population increase. Plant resistance researchers must employ genotyping by sequencing and high-throughput phenotyping to identify, map and track resistance genes. In contrast to maize, rice, vegetables and wheat, limited progress has occurred to develop meaningful levels of pest resistance in cassava, cowpea and pigeonpea - major sources of nutrition for nearly 1 billion people. A knowledge void exists about the effects of climate change (elevated CO2) on resistant plants, necessitating efforts to understand this stress. Collaborations with social scientists, extension specialists, economists, spatiotemporal modelers, ecologists, and virologists will be required to develop better ways to integrate insect resistant plants into integrated crop pest management programs.

Participatory Rural Appraisal on Cowpea Production Constraints and Farmers’ Management Practices in Burkina Faso

Success of cowpea cultivation requires a strong understanding of production constraints in order to overcome them. It is thus useful to know whether smallholder cowpea growers use modern or indigenous means to overcome these challenges. We completed a participatory rural appraisal (PRA) study to identify current cowpea production constraints and management practices in Burkina Faso. We interviewed 481 cowpea growers (219 women and 262 men) and used a mixed-method design of collecting both qualitative and quantitative data. The results showed that water scarcity, damage due to insects, plant diseases, striga, lack of training, and marketing challenges are the main constraints to cowpea production. Among insects reducing cowpea yield, growers identified aphids as a major pest. However, growers often did not know the biology and incidence of insects in their fields. This study also identified local resistant cowpea varieties in various locations.

Assessment of Striga gesnerioides (Willd.) Resistance and Genetic Characterization of Forty-Six Cowpea (Vigna unguiculata (L.) Walp.) Genotypes in Ghana

The parasitic weed, Striga gesnerioides, imposes physiological stress on cowpea (Vigna unguiculata (L.) Walp.) resulting in significant yield loss in the regions of northern Ghana. This warranted identification of resistant cowpeas for sustainable production. The current work aim was to identify Striga-resistant cowpea genotypes and assess their genetic relatedness. Forty-six (46) cowpea genotypes were screened in pots for their reaction to Striga samples obtained from the upper east, upper west, and northern regions of Ghana and validated with C42-2B and 61R-M2 markers involving DNA amplification by PCR assay. Sixteen polymorphic SSR primer pairs were used to assess genetic relatedness among 46 cowpea genotypes. Data were analyzed with PowerMarker V. 3.25 and a dendrogram was generated with MEGA 4. On the whole, 65.2% of the cowpea genotypes had stable resistance to S. gesnerioides from the regions of northern Ghana and 34.8% were susceptible. The C42-2B marker resolved as a single DNA band of 280 bp with segregation efficiency of 80% and 61R-M2 marker as double DNA bands of 320 bp and 380 bp with segregation efficiency of 60% associated with Striga resistance. Sixteen (16) polymorphic SSR primers distinguished all 46 cowpea genotypes into three clusters. Gene diversity ranged from 0.04 to 0.49 with an average of 0.29. The average allele frequency is 0.78, with a mean genetic diversity of 0.29. Polymorphism information content (PIC) varied from 0.08 to 1.00 with an average of 0.55. Therefore, cowpeas with Striga resistance and other desirable traits can be evaluated and released as varieties for farmers to cultivate.