The study was conducted to understand the yield and protein performance of Brazilian cowpea genotypes under diverse environments in Uganda. The grain yield and protein content varied based on the genotypes, environ- ments and their interactions. Although genotype C2T had the highest yield but it was only adapted to specific environments. Hence genotype C1J, which was equally high yielding, stable and adapted to the three environ- ments tested, should be recommended for cultivation in Uganda. In terms of environments, the best grain yield was obtained from Serere, which implied that this environment was favorable for growing Brazilian lines in Uganda. The interaction of genotype x environment also affected grain yield which implied that, the grain yield of cowpea differed based on different environmental factors (soil types and rainfall). Although, genotype C21 had the highest protein levels, it might not be the best genotype to grow as a high protein cowpea genotype in Uganda. This is because it is only adapted to specific environment, i.e. Serere. But genotypes such as C1J, C2Q and BRS Pujante which are high in protein and are adapted to three environments with high stability can be promoted in Uganda for human and animal consumption. However, we recommend that in the future the high protein content in C21 can be used by breeding program to improve protein content in Ugandan cowpea germplasm.
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Environmental coefficient of variation (CV e %), in general, indicated good experimental precision for all evaluated traits, since the magnitude of this parameter was less than 15%, except for the MSL, which obtained an estimate more than 20%. According to Cruz et al. (2012), values of CV lower than 20% denote excellent environmental control in phenotypic traits with continuous distribution. In this way, it can be affirmed that the experimental design used contributed to minimize the non-controllable effects. Teófilo et al. (2008), evaluating several traits in cowpea genotypes, observed estimates of CV varying from 4.34% (HGM) to 30.77% (YIE), while Silva and Neves (2011) found for YIE CV estimates of 45.98%, and in both cases the estimates for this trait were superior to those obtained in this study.
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The study was conducted at the Department of Crop Science, University of Ghana (UG), Legon. Fifty cowpea (Vigna unguiculata L.) genotypes were evaluated. The 50 cowpea genotypes included 18 early maturing, 6 medium maturing, 10 Striga resistant and 6 dual purpose genotypes obtained from Institute of Tropical Agriculture (IITA), and 10 from the Crop Science Department, UG. The latter from UG were improved varieties which have been released and grown extensively in most of the agro- ecological zones of Ghana. Seeds of each genotype were surface sterilized in 0.5% NaOCl for one minute rinsed and sown into PVC tubes of length 15.0 cm and 3.4 cm in diameter. The tubes contained a mixture of sawdust and rice husk in the ratio of 1:1 by volume. The tubes were placed in aluminium troughs containing 0.5 mM CaSO 4 solution. Each genotype was replicated six
Fusarium redolens, a virulent fungus which causes damping off, leaf yellow- ing, wilting and root rots has recently been devastating cowpea fields in Uganda. This study aimed at identifying cowpea genotypes that are resistant to Fusarium redolens. Therefore, ninety cowpea genotypes were evaluated two times against a highly virulent Fusarium redolens (isolate from Zombo in Paidha district) in the screen house in 2016. Genotype effect was highly sig- nificant (P < 0.001) for root rot severity. Based on the Index of Susceptibility (IS), three genotypes (Asontem, Dan1 LA and IT89KD-88) remained resistant (IS < 3.5) over the two screening periods, 72 moderately resistant (3.5 ≤ IS < 6.5) and 11 susceptible (IS ≥ 6.5). Resistance was found to be enhanced by presence of lateral roots above or at the ground level. Further results sug- gested a difference in genetic control of resistance to root rots and seed rots caused by Fusarium redolens . All the released varieties tested (SECOW 1 T, SECOW 2 W, SECOW 3 B, SECOW 4 W and SECOW 5 T) had moderate re- sistance to Fusarium redolens . Correlation analysis revealed root rot severity was strongly correlated to disease incidence (+0.64, P < 0.001), to proportion of plants with lateral roots (−0.56, P < 0.001), to amount of leaf chlorophyll (−0.53, P < 0.001) and to proportion of plants that died prematurely due to Fusarium redolens infection (+0.45, P < 0.001). No significant correlation was detected between root rot severity and proportion of plants that germinated. The established resistance could be exploited for improvement of farmer pre- ferred cowpea varieties towards Fusarium redolens resistance in Uganda.
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The experiments were laid out in a randomized complete block design in a split plot arrangement with two replications, two watering regimes as main plots and the test genotypes as subplots. The two water regimes were no stress (pot capac- ity-50% maximum water capacity) and severe stress. Eight seeds per each of the 30 cowpea genotypes and 7 drought tolerant checks were planted in the screen house in 10 litre-plastic pot perforated at the base and filled with 10 kg top soil and later thinned to 4 seeds per pot 8 Days after planting (DAP). The soil used was composed of 66% sand, 16% clay, 18% silt, 0.15% total nitrogen, 0.53 Cmoles/kg of potassium and 4.24 parts per million (ppm) of phosphorus. NPK fertilizer was applied to soil at the rate of 6 g/pot, based on soil analysis in order to provide the recommended nutrient requirement for cowpea . The NPK fertilizer was applied to each pot by incorporating it into the soil at planting to remove nutrient deficiency as a limiting factor .
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Parasitic angiosperm Alectra vogelii Benth is a growing problem in Malawi, particularly with current emphasis on legumes. Therefore, two studies were set in order to understand the possible mechanisms of resistance in cowpea genotypes on their reaction to the parasitic weed. In the first experiment, Mkanakaufiti , IT99K-7-21-2-2XIT82E-16, Sudan 1 and IT82E-16 were grown in Alectra infested and non-infested pots. The experiment (2*4 factorial treatment combination) was arranged in an RCBD and replicated eight times. The second experiment, involved Petri-dish techniques where 4 genotype roots were assessed on their ability to stimulate the germination of A. vogelii as a proxy for germination stimulant production. The experiment was ar- ranged in an RCBD and replicated five times. In the first experiment, data was collected on; the number of days to first Alectra emergence, Alectra shoot counts at 6, 8, 10, and 12 weeks after planting (WAP), Alectra attachment at 5 and 12 WAP, Alectra biomass at 12 WAP, cowpea biomass parameters at 5 and 12 WAP, yield and yield components per pot. While in the second expe- riment, number of germinated Alectra seeds per Petri dishes was recorded. The results indicated that IT82E-16 (33.25 days) and Sudan 1 (34.25 days) were earlier infested whilst late on IT99K-7-21-2-2XIT82E-16 (38 days) which correlated to the number of Alectra attachments. There were significant dif- ferences ( p = 0.05) in weekly Alectra counts between cowpea varieties from 6 up to 10 WAP. Mkanakaufiti and IT99K-7-21-2-2XIT82E-16 were observed with no and few Alectra shoots infestation respectively which was an indicator of resistance mechanism in the study. Number of pods, grain weight (g) and harvest index per pot were significantly affected by inoculation protocol with lower yield on infested cowpea genotypes. The same trend was observed on cowpea varieties where Mkanakaufiti (21.9 g/pot) shown higher yield followed by IT82E-16 (12.5 g/pot) which is susceptible but with tolerance ability to the parasitic weed. The study has shown that resistance mechanisms can be cate- How to cite this paper: Phiri, C.K., Ka-
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sensitive cowpea genotype than in the tolerant under saline stress condition. However, Ali and Komatsu (2006) found decreased Rubisco expression in rice (Oryza sativa L.), while Razavizadeh et al. (2009) verified increased expression in tobacco (Nicotiana tabacum) under saline stress. Moreover, Paiva (2015) observed reduced expression of Rubisco in cowpea under biotic and abiotic stresses compared to control conditions. It shows that this enzyme is subject to both increased and decreased expression under many stress conditions. Regarding the isoforms, the large subunit of Rubisco, partial (chloroplast), was identified in more than one spot (spots 26, 100 and 115). According to Hajheidari et al. (2005), the same protein present in different spots indicates higher protein degradation rates. Such modifications in Rubisco isoforms in genotypes under stress seem to be post- translational changes or other changes in gene expression that may play a role in acclimatization to water stress, and not necessarily related to stress tolerance (Mesquita et al., 2012).
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Salinity resulted in altered growth of cowpea due to its effects on the various physiological and biochemical parameters studied. Salinity increased lipid peroxidation leading to membrane imbalance and at the same time also reduced the uptake of important mineral elements. However, in the present study, AMF ameliorated the negative impact of salinity on growth and biochemical parameters. AMF allayed the salt stress by preventing the excess uptake of Na+ and at the same time causing further enhancement in activities of antioxidant enzymes thus ensuring better scavenging of ROS. Thus salinity induced toxic effects on growth, antioxidant enzymes and mineral nutrients in cowpea can be alleviated by AMF.
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The response of cowpea plants to water deficit depends on genotype, drought intensity, and the growth stage at which drought occurs. In our trial, the number of leaves per plant and dry matter of cowpea were negatively affected by water deficit at flowering, which manifested in up to 50% yield reduction when com- pared to well-watered plants. Similarly, the number of days to flowering and maturity were shortened by imposing terminal drought on the test cowpeas in this study. Genotypes PI339600, PI527263, PI527302, PI582793, PI582867 and SARI-6-2-6 have promising yield potentials under drought stress conditions. These genotypes could be exploited for future breeding program that will devel- op drought tolerant varieties for the savannah ecology of northern Ghana and other areas with similar environmental conditions across West Africa.
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The study has shown that some of the cowpea genotypes obtain from crosses between Apabaala (IT x P148-2), Marfo- Tuya (Sul 518-2) and UCRO 1-15-52 such as SARC 1- 132-1, SARC 3-90-2, SARC 1-91-1, SARC 1-13-2 and SARC 3-103-1 posses genes that confer some degree of resistance to C. maculatus. Significant differences among the genotypes were obtained for all the parameters used for the assessment, with the exception of the growth index. It has been reported that variables such as adult emergence, developmental period, weight loss and growth index are the most reliable indicators for resistance of cowpea to damage by C. maculatus (Redden and McGuire, 1983; Jackai and Asante, 2003). More eggs were deposited on the seeds of some moderately resistant genotypes such as Marfo-Tuya, SARC 4-75, SARC 1-71-2 and IT95K-193-2 than the most susceptible genotypes (Apabgaala) although adult emergence, seed weight loss and growth index were lower on these genotypes than that of Apabgaala. The suitability of cowpea seed type for oviposition by C. maculatus is influenced by surface area and curvature of the seeds (Avidov et al., 1965; Nwanze and Horber, 1976; Wasserman, 1981; Fitzner et al., 1985). Nwanze et al. (1975) reported that C. maculatus prefers smooth-coated and well-filled seeds to their rough and wrinkled counterparts for oviposition. Mbata (1992) also reported that the surface area of cowpea seeds varies among varieties, and number of eggs laid per seed is positively correlated with the surface area. Although the surface area and the smoothness of seed coat were not determined in the present study, these factors may well explain why eggs were not equally distributed among seeds of the different cowpea genotypes used. On the other hand, both adult emergence and seed weight loss were found
tween %N and %C in shoots of the test cowpea genotypes evaluated in both lo- cations. Of the 25 genotypes evaluated, only PI121433 recorded lower C/N ratio at Kpachi relative to its counterpart at Woribogu, as opposed to lower C/N ratio recorded by genotypes PI162924, PI186386, PI194211 and PI209971 at Woribo- gu when compared to their respective counterparts at Kpachi (Figure 5(c)). Ex- cept for the five genotypes which exhibited differences in C/N ratio between lo- cations, the remaining genotypes recorded similar values regardless of planting location (Figure 5(c)). In general, the C/N ratio of the test cowpeas were low in both locations, with values ranging from 11.3 g/g to 18.6 g/g at Kpachi and 10.8 g/g to 16.3 g/g at Woribogu (Figure 5(c)). Although the average %N was similar between locations (Table 1), the plants at Kpachi recorded higher shoot C con- centration leading to much lower C/N ratio relative to plants grown at Woribo- gu (Table 2).
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A greenhouse pot experiment was conducted at the University of Zimbabwe to screen six cowpea varieties for resistance to Alectra vogelii infection. Emergence of A. vogelii was first detected 55 days after crop emergence. A. vogelii emergence was not significantly (P > 0.05) influenced by cowpea genotype. No differences (P > 0.05) in cowpea parameters that were measured were observed among the cowpea genotypes. However, A. vogelii infection significantly (P < 0.05) reduced cowpea shoot biomass and pod number by 57 % and 98 %, respectively. Infected cowpeas failed to produce any pods at all with the exception of cowpea cultivar C/83/4/6 and C/85/6/4. A similar trend of results was observed with grain yield. Root biomass was not significantly influenced by A. vogelii infection. A. vogelii infected cowpeas had significantly (P < 0.05) higher root /shoot ratio compared to uninfected plants. Based on results on A. vogelii emergence and cowpea parameters collected in this study, it can be concluded that all the cowpea genotypes evaluated are susceptible to A. vogelii infection. However, it can also be concluded that the two pre-released varieties C/83/4/6 and C/85/6/4 are moderately susceptible because they were able to produce grain and should therefore be further evaluated under field conditions.
Forty cowpea genotypes were evaluated for 18 quantitative characters to estimate the genetic diversity existing among them by using Mahalanobis D 2 statistics. The genotypes were grouped into six clusters. The cluster strength varied from single genotype (Clusters III, IV and V) to 25 genotypes (Cluster I). Clusteres IV and VI had high inter cluster distance. Clusters II, III and I had maximum 100-seed weight, number of seeds per pod and seed yield respectively. Cluster IV had maximum seedling vigour index, germination per cent, peduncle length, number of clusters per plant and number of primary branches. The genotypes from clusters IV and IV may be inter crossed to obtain high variation.
Cowpea is widely grown in the humid tropics as a staple, however, in this region, it is largely affected by genotype by environment interaction (GEI), making it difficult and expensive to select and recommend new genotypes for different environments. The nature, magnitude and effects of genotype by environment interaction (GEI) on the growth and yield characters cowpea varieties in early- and late- rainy seasons, at 2 locations (Akure and Ado Ekiti ) and 3 years (2013-2015) was quantified. The results depicted differential performance of cowpea genotypes at different test environments and hence the interaction was crossover type. The GEI explained about 60 % of the variation which is more than double of the environmental and four times of the genotypic effects of the total variation. Varieties Oloyin Brown, IT97K-568-18 and IT98K-573-2-1 exhibited both high yield and stability across the test environments and could be characterized as ideal while the most unstable varieties with poor performance are IT98K-205 and IT96D-610. The study identified superior cowpea genotypes for tested locations (Akure and Ado Ekiti environments) an information which denotes the value of the tested locations for future cowpea breeding activities. It is concluded that cowpea varieties produced high seed yield as early and late rainy season crops at both locations. Ado-Ekiti location was best for the late rainy season while Akure location was best for the early rainy season.
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Random Amplified polymorphic DNA (RAPD) is used to determine genetic diversity of cowpea genotypes collected from different regions of India. A high diversity within population and high genetic differentiation among them were analyzed. Total 194 bands were generated among them 152 bands were found polymorphic with an average 7.6 bands per primer. The average percentage of polymorphism across 20 primers was 78.83 %. A high level of average genetic diversity was observed. A dendrogram produced by the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) based on Jaccard‟s similarity coefficient revealed two groups. The overall range of genetic similarities ranged from 0.533 to 0.790 in 20 genotypes of cowpea which indicates there was high variability among the genotypes. Based on genetic distance in RAPD analysis the genotypes viz., C-152, PGCP-11 and PGCP-6 appeared as most divergent and could be used in breeding programme of cowpea. Our results indicate that RAPD approach analysis seemed to be best suited for assessing with high accuracy the genetic relationships among distinct cowpea genotypes.
Drought tolerant cowpea germplasm would offer potential solutions to challenges associated with low production in drought prone areas. This research characterised 36 accessions for canopy maintenance in a glasshouse, as a first step towards the identification of drought tolerant cowpea genotypes in Malawi. Canopy responses were scored using the International Board for Plant Genetic Resources (IBPGR) and Mai-Kodomi leaf wilting scales, relative water content (RWC) and leaf wilting index (LWI) after withdrawing water for four weeks. Re-growth and stem greenness were scored after the second week of re-watering. The reduction of soil moisture content from 26.2% to 2.9% provided sufficient stress over a period of four weeks to identify drought tolerant genotypes. The accessions showed highly significant variations (P=0.0001) for all the variables indicating that some accessions survived the low soil moisture level better than others. Accessions 479, 601, 645, 2226 and 3254 showed high RWC, low values on wilting scales and wilting index, high scores of stem greenness and apical re-growth in contrast with accessions 517, 2231, 2232, 2883 and 3215. Cluster analysis grouped the accessions into five distinct clusters with accessions 479, 601, 645, 2226 and 3254 in Cluster 4 and accession 2232 in its own Cluster 5. Clusters 1, 2 and 3 comprised 14, 12 and 4 accessions, respectively. Cluster 4 was strongly associated with apical re-growth, high RWC, high scores of stem greenness, and low scores for both leaf wilting scales and LWI as opposed to Clusters 5 and 1. The correlation analysis revealed highly significant positive and negative relationships between LWI and the commonly used traits in screening for drought tolerance, thus indicating the prospects of using LWI in screening cowpea germplasm to overcome limitations associated with leaf wilting scales. The genotypes in Clusters 4 and 5 require further study in order to understand the physiological mechanisms governing their responses.
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The assessment of protein content in cowpea is of interest in order to identify geno- types with high protein content. Itatat et al.  assessed eleven cowpea genotypes for seed protein content. Their results revealed that the seed protein content of those cow- pea lines ranged from 20.57% to 24.95%. Research performed by Afiukwa et al.  on 110 cowpea genotypes exhibited a greater variability than what Itatat reported . Afiukwa et al.  have found that the total seed protein content for their genotypes varied from 15.06% to 38.5%, with a mean of 25.99% ± 4.82% in dry seeds. Oke et al.  analyzed the protein content in five varieties of cowpea and found that the protein content ranged from 25.80% to 28.95%. Moreover, protein fractions viz. albumins, globulins, prolamins and glutelins of cowpea genotypes showed significant differences according to a study by Gupta et al. . Their analysis on molecular weights of protein bands from 11 cowpea genotypes using SDS-polyacrylamide gel electrophoresis dis- played a variation between 10 to 141.3, 15.85 to 147.9, 10 to 125.9, 7.94 to 56.23 and 10 to 79.43 kDa for total proteins, albumins, globulins, prolamins, and glutelins, respec- tively.
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Most protease trypsin is thermolabile. The content of trypsin and chymotrypsin in cowpea seeds could be reduced during the cooking. It was showed that trypsin inhibitor activity in soybeans was reduced of 26.3% during heat- treatments . Trypsin inhibitors from Leguminosae seeds are reported to be great thermo resistance to high temperatures . The reduction or elimination of enzyme inhibitors of pulses could be made using different food processes, like dehulling, soaking, boiling, roasting, autoclaving, micronization, microwave cooking, extrusion cooking, fermentation and germination . It will be interesting to study the effect of these different food processes in trypsin and chymotrypsin inhibitors content of cowpea seeds. The PCA components analysis and the dendrogram constructed divided the thirty-one genotypes of cowpea used in this study into three class according to their protease inhibitory activities. The cowpea genotypes of class I possess the highest inhibitory activity of chymotrypsin as compared to trypsin inhibitory activity and at least 50% inhibition of proteases. The class II genotypes showed the high inhibitory activity of trypsin as compared to chymotrypsin inhibitory activity. The genotypes belonging to class III possess the highest inhibitory activity of chymotrypsin as compared to trypsin inhibitory activity and less than 50% inhibition of proteases. This study suggests that it will be possible to breed the cowpea with low or high inhibition potential of protease enzymes.
The most common method of screening cowpea genotypes for drought tolerance has been the use of: visual symptoms of wilting, plant death and recovery (Watanabe, 1998b; Watanabe & Terao, 1998; Mai-Kodomi et al., 1999a,b; Singh et al., 1999a,b; Muchero et al., 2008), physiological and morphological responses (Chiulele & Agenbag, 2004), morphological and yield response of genotypes under stressed and non-stressed conditions (Matsui & Singh, 2003). This requires therefore, the identification of specific traits under adequate moisture that are easy to measure and are associated with drought tolerance (Fischer and Wood, 1979). Furthermore, in plants, a better understanding of the morpho-anatomical and physiological basis of changes in water stress resistance could be used to select or create new varieties of crops to obtain a better productivity under water stress conditions (Nam et al., 2001; Martinez et al., 2007).
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Abstract: The demand for cowpea (Vigna unguiculata L. Walp) is higher than supply in Ghana due to low yields caused by pathogenic diseases, predominantly rust disease. The use of rust resistant cultivars is the most effective method to control cowpea rust. Genetic variations among cowpea genotypes may be potential sources of rust resistance to control cowpea rust and increase cowpea yield and production in Ghana. The study assessed rust disease incidence and severity among cowpea genotypes and determined resistance to cowpea rust under field conditions. Twenty-four cowpea genotypes were sowed in four agro-ecological zones in two cropping seasons in Ghana. Cowpea rust incidence, severity, area under disease progress curve (AUDPC) and relative area under disease progress curve (rAUDPC) were significantly (p < 0.05) higher in the semi-deciduous forest and minor cropping season compared with deciduous forest, coastal savannah, Sudan savannah and major cropping season. The cowpea genotypes also showed significant differences (p < 0.05) in response to rust infection. Positive and negative correlations existed in rust incidence, severity, AUDPC and rAUDPC within the agro-ecological zones and cropping seasons. The differences observed were due to variations in climatic conditions and genetic composition of the cowpea genotypes. Five cowpea genotypes were better slow rusting, eleven cowpea genotypes were slow rusting and eight cowpea genotypes were fast rusting. Interestingly, eleven cowpea genotypes showed resistance and eight cowpea genotypes showed moderate resistance to cowpea rust. The rust resistant cowpea genotypes identified in this work can be recommended for farmers to cultivate and used in breeding programmes to further improve the crop. This will maximize yields and increase cowpea production particularly in rust prone areas.