Literatura académica sobre el tema "Cowpea – Diseases and pests – 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.

Losses caused by flower thrips in cowpea are important. These pests can cause from 60% to total crop yield loss. There is, therefore , an urgent need to address this issue. This work has been undertaken to identify sources of resistance to thrips in cowpea. Twenty cowpea genotypes were screened at Kamboinsé research station under improve netting in pots. The number of aborted flowers per line, the percentage of damage to flowers and stipules, and the number of thrips per genotype were evaluated. The results revealed the existence of six genotype of cowpea resistant to thrips. Among these genotypes three are already known thrips resistant lines (TVU1509, TVx3236 and Sanzi). Moreover, Sanzi showed interesting potentialities that maybe exploited. The new identified lines are Nafi, variety popularized in 2012 and variety KVx780-3 which is being popularized. The KVx165-14-1 (old popular variety) showed sources of tolerances while the KN1 genotype was susceptible to thrips. In another hand, all the wild genotypes showed high susceptibility to thrips.

Antioxidant compounds of dietary plants have been widely studied because of their bioactive properties. The objective of this research study was to analyse the health enhancing attributes of 31 cowpeas varieties from Burkina Faso. Significant variations were observed in the phenolic content as well as the antioxidant and anti-lipid peroxidation activities amongst the cowpea varieties. Pearson correlation coefficient analysis showed that the ferric reducing ability (r = 0.954) and anti-lipid peroxidation (r = 0.616) were positively correlated with the total phenolic content. A significant relationship between cowpea ferric reducing ability and anti-lipid peroxidation (r = 0.64) was also revealed. However, nitric oxide scavenging potential was found not to be related to its total phenolic and total flavonoid content. 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals scavenging potentials were not correlated with the total flavonoid content. The pigmented seeds of cowpea varieties possess higher total phenolic, total flavonoid content, ferric reduction ability, and anti-lipid peroxidation activities than the colourless ones. The results obtained from this study suggest that Burkina Faso cowpea cultivars are rich in phenolic compounds and have significant antioxidant and anti-lipid peroxidation activities. Consumption of the cowpea, particularly of coloured cowpea seed varieties, should be beneficial for chronic human diseases prevention.

Abstract Cowpea [Vigna unguiculata (L) Walp.] is an important staple legume in the diet of many households in sub-Saharan Africa. Its production, however, is negatively impacted by many insect pests including bean pod borer, Maruca vitrata F., which can cause 20–80% yield loss. Several genetically engineered cowpea events that contain a cry1Ab gene from Bacillus thuringiensis (Bt) for resistance against M. vitrata were evaluated in Nigeria, Burkina Faso, and Ghana (West Africa), where cowpea is commonly grown. As part of the regulatory safety package, these efficacy data were developed and evaluated by in-country scientists. The Bt-cowpea lines were planted in confined field trials under Insect-proof netting and artificially infested with up to 500 M. vitrata larvae per plant during bud formation and flowering periods. Bt-cowpea lines provided nearly complete pod and seed protection and in most cases resulted in significantly increased seed yield over non-Bt control lines. An integrated pest management strategy that includes use of Bt-cowpea augmented with minimal insecticide treatment for protection against other insects is recommended to control pod borer to enhance cowpea production. The insect resistance management plan is based on the high-dose refuge strategy where non-Bt-cowpea and natural refuges are expected to provide M. vitrata susceptible to Cry1Ab protein. In addition, there will be a limited release of this product until a two-toxin cowpea pyramid is released. Other than South African genetically engineered crops, Bt-cowpea is the first genetically engineered food crop developed by the public sector and approved for release in sub-Saharan Africa.

AbstractThe legume pod borer, Maruca vitrata, is an endemic insect pest that causes significant yield loss to the cowpea crop in West Africa. The application of population genetic tools is important in the management of insect pests but such data on M. vitrata is lacking. We applied a set of six microsatellite markers to assess the population structure of M. vitrata collected at five sites from Burkina Faso, Niger and Nigeria. Observed polymorphisms ranged from one (marker 3393) to eight (marker 32008) alleles per locus. Observed and expected heterozygosities ranged from 0.0 to 0.8 and 0.0 to 0.6, respectively. Three of the loci in samples from Nigeria and Burkina Faso deviated significantly from Hardy-Weinberg Equilibrium (HWE), whereas no loci deviated significantly in samples from Niger. Analysis of molecular variance (AMOVA) indicated that 67.3% level of the genetic variation was within individuals compared to 17.3% among populations. A global estimate of FST=0.1 (ENA corrected FST=0.1) was significant (P⩽0.05) and corroborated by pairwise FST values that were significant among all possible comparisons. A significant correlation was predicted between genetic divergence and geographic distance between subpopulations (R2=0.6, P=0.04), and cluster analysis by the program STRUCTURE predicted that co-ancestry of genotypes were indicative of three distinct populations. The spatial genetic variance among M. vitrata in West Africa may be due to limited gene flow, south-north seasonal movement pattern or other reproductive barriers. This information is important for the cultural, chemical and biological control strategies for managing M. vitrata.

Alectra vogelii Benth. (Family: Scrophulariaceae) is a vascular hemiparasite of various leguminous crops in Africa, including peanut (Arachis hypogaea), bambara groundnut (Vigna subterranea), cowpea (Vigna unguiculata), common bean (Phaseolus vulgaris), soybean (Glycine max), and mung bean (Vigna radiata) (1). It is a common parasite of peanut in Angola, Burkina Faso, Malawi, Mozambique, Nigeria, Swaziland, Zambia, and Zimbabwe (2). During April and May 2000, A. vogelii was observed parasitizing several wild Arachis species in a field at the Chitedze Agricultural Research Station near Lilongwe, Malawi. These species were part of a germ plasm enhancement program that included A. appressipila (ICRISAT Groundnut Accession number [ICG] 8127), A. batizocoi (ICG 8124), A. benensis (ICG 13215), A. cardenasii (ICG 13164 and 13166), A. correntina (ICG 8918), A. duranensis (ICG 13200), A. helodes (ICG 8955 and 14917), A. hoehnei (ICG 13228), A. magna (ICG 8960), A. pintoi (ICG 13222 and 14914), A. stenosperma (ICG 13172 and 13223), and A. valida (ICG 13230). In addition, A. vogelii was observed on four unidentified Arachis species (ICG 13231, 14875, 14888, and 14907). Parasitized plants were less vigorous and connections between A. vogelii and host plants could be observed by carefully removing the soil in the root zone. Mature A. vogelii plants were 0.3 to 0.5 m and had multiple stems branching at the base. Subsoil plant parts were a deep orange color. Flowers were prominent lemon yellow with horseshoe-shaped stigmata and leaves were light green. This is the first report of A. vogelii parasitizing wild Arachis species. References: (1) C. Parker. Crop Prot. 10:6–22, 1991. (2) P. Subrahmanyam. 1997. Parasitic flowering plants. Pages 70–71 in: Compendium of Peanut Diseases, 2nd Ed. N. Kokalis-Burelle, D. M. Porter, R. Rodriguez-Kabana, D. H. Smith, and P. Subrahmanyam, eds. American Phytopathological Society, St. Paul, MN.

AbstractThe 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.

Field and laboratory investigations were conducted in Burkina Faso to diagnose the causes of severe outbreaks of Bemisia tabaci populations and gênerai failures of chemical control against this pest in cotton.
Field and laboratory investigations were conducted in Burkina Faso to diagnose the causes of severe outbreaks of Bemisia tabaci populations and general failures of chemical control against this pest in cotton. The research efforts were oriented in the following three areas: I) the susceptibility of B. tabaci populations and its parasitoids to cotton insecticides; I) the susceptibility of B. tabaci populations and its parasitoids to cotton insecticides, a) conventional insecticides, b) novel insecticides; II) the relative abundance of B. tabaci and its parasitoids in the field; III) the biological activities of some botanical extracts as alternative insecticides against the pest.

A four-year (1988 to 1991 inclusive) field and laboratory study was undertaken to determine and select the components that could be integrated to control the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso, West Africa. Nine approaches were investigated: (1) monitoring adult shoot flies; (2) sequential sampling based on egg and dead heart counting; (3) cultural practices (sowing dates and plant densities, intercropping sorghum-cowpea); (4) use of resistant cultivars; (5) use of natural insecticide from the neem tree Azadirachta indica A. Juss. (Meliaceae); (6) effects of intercropping sorghum-cowpea on the natural enemies of the shoot fly; (7) spider fauna in pure sorghum and intercropped sorghum-cowpea; (8) parasitism of the shoot fly by a larval parasitoid, Neotrichoporoides nyemitawus Rohwer; and (9) the biology of an egg parasitoid, Trichogrammatoidea simmondsi Nagaraja. These nine approaches were divided into four main components: (1) monitoring populations, (2) cultural practices, (3) natural and chemical pesticides, and (4) biological control that could be integrated to control the shoot fly. Among these components, monitoring populations (egg sampling), cultural practices, and use of natural pesticides could be utilised at the farmer level.

In Burkina Faso, the existence of different races of Striga gesnerioides (Willd.) Vatke, with apparent variable aggressiveness on cowpea (Vigna unguiculata (L.) Walp) renders the breeding task very complex. Therefore, a number of studies was carried out from 2006 to 2009 in field, pot and ‘’in-vitro’’ to identify new sources of resistance to three prevailing Striga races, SR 1, SR 5 and a newly occurring Striga race named SR Kp and to understand the genetic pattern of the underlying resistance of cowpea germplasm to Striga races found in Burkina Faso. To achieve these objectives, the following investigations were initiated: (i) a participatory rural appraisal (PRA), a participatory variety selection (PVS) and grain quality survey were implemented to identify cowpea breeding priorities for Burkina Faso Striga hot-spots; (ii) the identification of sources of resistance in Burkina Faso germplasm, using three prevailing Striga races of S. gesnerioides as sources of inoculum; (iii) the identification of the mechanisms of resistance underlying the resistance to Striga in such genotypes; (iv) a study of combining abilities of selected parents through a diallel cross; (v) a study of the segregation patterns in crosses involving resistant and susceptible sources and a study of the allelic relationships between different resistance sources. The participatory studies conducted in 2007 and 2008 over three districts in Striga hotspots; there was no effective control method against Striga at farmers’ level. These investigations highlighted the importance of cowpea across all sites. Rain decline over time, low input use coupled with a poor extension system were the major constraints mentioned by farmers. Differential reactions of genotype KVx61-1 for Striga resistance suggested that different Striga races were prevailing in different areas. Farmers’ preferred traits in cowpea genotypes were oriented towards grain quality such as big sized grain, white seed colour and rough texture of cowpea grain, except in Northern-Burkina Faso, where farmers preferred brown-coloured grain for food. Cowpea was also seen as an income generating crop. An evaluation of 108 genotypes was done in 2007 in the field (rainy season) and in pots (off-season) for Striga resistance assessments. The screening trials enabled the identification of sources of resistance to S. gesnerioides. Genotypes KVx771-10, IT93K- 693-2, KVx775-33-2, Melakh and IT81D-994 are potential sources of resistance to all three Striga races with acceptable yield. Landraces were susceptible and late-maturing whilst most wild species were resistant but with unwanted shattering traits. A combining ability study for Striga resistance parameters conducted in pots and a resistance mechanism study conducted ‘’in-vitro’’ were performed using F1 populations from a 10 x 10 diallel cross. The general combining ability (GCA) effects were significant for the resistance parameters Striga emergence date (DSE), Striga height above soil (SH), cowpea grain weight (CGW), hundred grain weight (HGW) for all Striga races involved and Striga vigour (SVIG) for SR 5 and SR Kp. The pot-screening showed that, regardless of the SR used as inoculum, the additive genes were important in conferring Striga resistance for parameters DSE, SH, CGW and HGW. The selection of parents could therefore result in breeding advance. Complete dominance, partial, over-dominance and non-allelic interactions (epistasis or failure of some assumptions) were present for some parameters. The ‘’in-vitro’’ screening showed that additive genes were important, with high narrow sense heritability values for the resistance mechanisms Striga seed germination frequency (GR) for SR 1 and SR Kp, the frequency of Striga radicle necrosis before the penetration in cowpea rootlet (NBP) for SR 5, the frequency of Striga radicle necrosis after the penetration in cowpea rootlet (NAP) for SR 1 and SR Kp and the susceptibility ‘’in-vitro’’ (SIV) for SR 5 and SR Kp. The selection of parents can be useful in accumulating the genes for Striga resistance mechanisms in progenies. The F2 populations derived from crosses between Striga-resistant x susceptible genotypes were evaluated in Striga infested benches in 2008 and 2009. The segregation patterns suggest that single dominant genes govern Striga resistance. The test for allelism showed that two non-allelic genes were responsible for the resistance to S. gesnerioides in cowpea. A new Striga resistance gene seems to be involved in genotype KVx771-10 resistance to S. gesnerioides, which confers resistance to all studied Striga races. Gene 994-Rsg in genotype IT81D-994 which confers Striga resistance to SR 1 and gene Rsg 3 also conferring Striga resistance to SR 1 segregated differently for the resistance to SR 5 suggesting that they were different but both confer resistance to SR 5.

The main goals of this study were to ascertain farmers' preferred traits in rice landraces and their perception of Rice yellow mottle virus, to collect rice landraces across Burkina Faso, investigate their genetic diversity, and to exploit this diversity in a search for varieties resistant and tolerant to RYMV, for their utilisation in rice breeding. Farmers' preferred traits, approaches to crop management, and disease perceptions were assessed using a Participatory Research Appraisal (PRA) approach. In the main rice growing regions of Burkina Faso, 330 rice landraces were collected. The agro-morphological diversity of the germplasms was evaluated in the field with 20 quantitative and 30 qualitative agro-morphological parameters. Thereafter, 22 Simple Sequence Repeat molecular markers were used to assess the genetic diversity and the population structure of the collection. Finally, the rice landraces were screened against four RYMV isolates to assess the susceptibility, tolerance and resistance of the landraces in the collection using visual assessment and Enzyme Linked Immunosorbent Assay. The PRA identified sweet taste, grain expansion when cooking, easy cooking and yield as paramount selection criteria in rural rice farming communities in Burkina Faso. Drought and disease resistance are characters that farmers wish to have in their varieties. The PRA also highlighted that farmers are conscious of RYMV disease in their fields. However, they are unaware about the epidemiology of the disease. An agro-morphological study of the phenotypic diversity of the collection confirmed the presence of the two cultivated rice species: O. glaberrima and O. sativa. There were more O. sativa accessions than O. glaberrima landraces. There were 48 O. glaberrima and 282 O. sativa accessions in the collection. Both species were divided into four clusters, reflecting the richness of the collection. The underlying genetic diversity of the collection was confirmed by the use of 22 Simple Sequence Repeat molecular markers. The neutral markers confirmed the existence of two substructures, namely O. glaberrima and O. sativa, and the presence of admixture varieties. However, a core collection of 52 individuals was developed. This included 13 O. glaberrima and 39 O. sativa accessions. It reflects the genetic diversity of the sub-clusters present in each species. This core collection contains 89% of the allelic richness of the collection. Its small size will facilitate the maintenance and active use of diversity of germplasm in the core collection. The entire collection was utilised to search for varieties resistant and tolerant to RYMV disease. The screening of the collection with different RYMV isolates exposed the susceptibility of most of the accessions in the collection. Most of the O. sativa indica accessions were highly susceptible. However, ten O. glaberrima accessions displayed a delay of symptom expression, and moderate resistance. However, their resistance was overcome later by a particularly virulent RYMV isolate BF1. Remarkably, a single moderately resistant cultivar, BM24, showed that partial resistance and tolerance to RYMV can be found in an O. sativa variety. Serological evaluation of this local variety in comparison with the partially resistant variety, Azucena, showed that BM24 and Azucena expressed similar resistance patterns. A genetic profile of both varieties showed that both had an identical allele status at RM101, which is a marker bracketed in the same zone as the QTL12.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.