Cowpea Leaf Research Articles

First report of Boeremia exigua causing spot blight on cowpea in China.

Cowpea or black-eyed pea [Vigna unguiculata (L.) Walp.] is a dual-purpose leguminous crop grown for food and fodder. In September 2022, cowpea plants exhibiting symptoms of a leaf spot and blight were observed in Renda Town located in Jingning County of Gansu Province, China, with the disease incidence in individual cowpea fields as high as 100%. Diseased leaves showed variable-sized, nearly circular brown blotches, large blotches with dark brown margins, and the adaxial surfaces of blotches had small black dots and whorls (Fig. 1). Multiple isolates with consistent colony characteristics were obtained from cowpea leaves with typical symptoms. The isolates were transferred to fresh potato dextrose agar medium (PDA) and then purified by transferring hyphal tips to PDA. Three isolates, JNJD-1, JNJD-2, and JNJD-3, were selected for subsequent identification and pathogenicity determination. After eight days at 25℃ on PDA, the colonies appeared irregular, aerial mycelium dense, cottony, atrovirens to olive brown, with white hyphae on the undulate margin (Fig. 2A and B). The pycnidia were globose to sub-globose, brown to dark brown, with 70-110 μm diameters. Single celled hyaline conidia were ellipsoidal to oblong with obtuse ends, and measured 6.6-9.3 × 2.8-4.1 μm (x̄ = 7.8 × 3.5 μm, n = 50) (Fig. 2C). Morphological characteristics are similar to the description of the genus Boeremia (Aveskamp et al, 2010). Primer pairs ITS1/ITS4, LR0R/LR5, fRPB2-5F2/fRPB2-7cR, and TUB2FD/TUB4RD were used to amplify portions of the ITS, LSU, RPB2, and TUB genes, respectively (Chen et al, 2015). The obtained sequences (Accession numbers: PP033662 to PP033664 for ITS, PP033667 to PP033669 for LSU, PP035531 to PP035533 for RPB2, and PP035534 to PP035536 for TUB) were 97% identical to that of a B. exigua strain CBS 431.74 (accession no. FJ427001, EU754183, GU371780, and FJ427112) (Table 1). The constructed maximum likelihood tree indicated close relationships between three isolates and B. exigua, which clustered together (Fig. 3). Cowpea plants (cultivar Junlintianxia) at the three-leaf stage were inoculated by spraying a spore suspension (1×106 conidia/ml) of JNJD-1, JNJD-2, and JNJD-3 until run off and incubated at greenhouse conditions (25°C and 12 h light). Inoculations with sterile water were used as a control and each treatment was repeated 3 times with five plants per replicate. Small brown spots appeared on the infected leaves at 2 dpi, followed by the appearance of large blotches, with dark brown at the margin and grayish-white in the center at 5 dpi (Fig. 4A). These lesions gradually increase and coalesce, causing leaf chlorosis and finally defoliation in serious cases. Disease incidence in inoculated cowpea plants treated with the isolates JNJD-1, JNJD-2, and JNJD-3 reached almost 100%. In contrast, control plants developed no symptoms (Fig. 4B). The pathogens were re-isolated from the inoculated leaves and identified as B. exigua using morphological and molecular analysis, whereas no fungus was isolated from control leaves. The experiment was repeated once under the same conditions, yielding similar results. B. exigua has a broad host range, infecting 19 families and 31 genera of plant species, and causing leaf spots, leaf blight, and tuber rot (Lan and Duan 2022). To our knowledge, this is the first report of the pathogen B. exigua causing spot blight on cowpeas. It has been reported that B. exigua infects leguminous crops from multiple genera, such as field pea, soybean, white clover, and Dumasia villosa (Liu et al, 2023). This study further enriches the host range of this pathogen and the pathogen species of cowpea leaf diseases.

Assessing the Effectiveness of Neem oil and Microalgae in the Management of Cowpea (Vigna unguiculata L.) Leaf Spot Caused by Alternaria spp.

The current study aimed to assess the effectiveness of neem oil and microalgae in controlling leaf spot caused by Alternaria spp. in cowpea (Vigna unguiculataL.). The research was conducted during the Zaid season of 2022 at the Central Research Field of the Department of Plant Pathology, SHUATS, Prayagraj, Uttar Pradesh, using a Randomized Block Design with three replications and seven treatments. Analysis of variance (ANOVA) was utilized to draw conclusions from the data. Leaf spot disease caused by Alternaria spp poses a significant threat to cowpea crops, resulting in yield losses and decreased plant vigor. An in vivo study was carried out to evaluate the impact of different concentrations of microalgae combined with neem oil at 1% on plant growth parameters and Disease Intensity (%). The application of microalgae @540 grams in various splits and neem oil @1% was done. Among all the treatments, T4 (Microalgae 48gms @5 DAS 96gms@15,45 DAS + Neem oil @1% showed promising results. Notably, the T4 treatment significantly increased plant height (84.63 cm) and the number of branches(10.83) at60DAS. Moreover, an increased numberof nodules per plant (21.44) was observed at 75 DAS, indicating improved root health and nitrogen fixation. Additionally, the treatment led to longer pod length (34.44 cm) in three pickings, suggesting enhanced yield potential. Furthermore, the combined application of microalgae and neem oil resulted in a significant reduction in disease intensity, with a notable decrease of 24.47% compared to untreated plants and those treated with chemicals (Bavistin). This indicates that the use of microalgae and neem oil together effectively suppressed leaf spot disease caused by Alternaria spp. in cowpea, thereby improving plant health and productivity. In conclusion, these findings underscore the potential use of eco-friendly alternatives like microalgae and neem oil for managing leaf spot disease in cowpea cultivation. Further research in this area is recommended for sustainable agricultural practices.

Iron Bioavailability and Functional Properties of cowpea leaf Powders : Potential to Improve Iron Intake Among Women of Reproductive Age in Ghana

Iron Bioavailability and Functional Properties of cowpea leaf Powders : Potential to Improve Iron Intake Among Women of Reproductive Age in Ghana

Effect of Harvesting Stage and Drying Method on Cowpea Leaf Nutrient Composition

Cowpea leaves are lost annually due to infestation and spoilage when being transported to clients and the losses at the local markets are brought on by inadequate postharvest handling procedures and market glut, particularly during peak seasons. High moisture content from the cowpea leaves at harvest stage may contribute to increased spoilage hence lowering quantity and quality. The choice of appropriate harvesting stage and drying method can help to reduce this problem. The aim of this study was to determine the best harvesting stage and efficient drying method that would maintain high leaf nutrient composition. Cowpeas variety M66 was used for the research and the treatments included three harvesting stages (21, 35 and 49 days after sowing [DAS]), three drying methods (open sun, solar dryer and oven. Data was collected on iron, calcium, crude fibre, beta carotene, protein and moisture content. The data was subjected for variance using Statistical Analysis System 9.2 edition and significantly different means separated using least significant difference at 5%. The results indicated significant (p<0.05) differences in moisture, calcium, proteins, beta carotene and crude fibre content in both trials. Harvest stage and drying method did not significantly (p<0.05) influence the iron content. Oven and solar drying methods showed better nutrient and mineral retention in the three harvesting stages when compared to the open sun drying method.

Effect of Harvesting Stage on Cowpea Leaf Nutrient Composition

Effect of Harvesting Stage on Cowpea Leaf Nutrient Composition

Influence of Fermentation on Functional Properties and Bioactivities of Different Cowpea Leaf Smoothies during In Vitro Digestion.

This study investigated the effects of Lactiplantibacillus plantarum 75 (LAB 75) fermentation at 37 °C for 48 h on the pH, total soluble solids (TSS), colour, total titratable acidity (TTA), carotenoids, and bioactivities of cowpea leaf smoothies from three cultivars (VOP 1, VOP 3, and VOP 4). Fermentation reduced the pH from 6.57 to 5.05 after 48 h. The TTA increased with the fermentation period, whilst the TSS reduced. Fermentation of the smoothies resulted in the least colour changes (∆E) in VOP 1 after 48 h. Fermentation of cowpea smoothies (VOP 1, VOP 3, and VOP 4) improved the antioxidant capacity (FRAP, DPPH, and ABTS), which was attributed to the increase in total phenolic compounds and carotenoid constituents in all of the fermented cowpea smoothies. VOP 1 was further selected for analysis due to its high phenolic content and antioxidant activity. The VOP 1 smoothie fermented for 24 h showed the lowest reduction in TPC (11%) and had the highest antioxidant (FRAP, DPPH, and ABTS) activity. Ltp. plantarum 75 was viable and survived the harsh conditions of the gastrointestinal tract, and, hence, could be used as a probiotic. VOP 1 intestinal digesta showed significantly higher glucose uptake relative to the undigested and the gastric digesta, while the gastric phase had higher levels of α-amylase and α-glucosidase compared to the undigested samples.

A benefit-cost analysis approach for determining the optimal processing of micronutrient-enriched cowpea leaf soup mixes

Cost-effective techniques are usually recommended in the dissemination and adoption of postharvest processing technologies of food products. Due to limited value addition practices for cowpea leaf, the Fruits and Vegetables for All Seasons Project undertook a study to bridge the gap in the seasonal availability of the vegetable in the arid and semi-arid lands (ASALs) of Kenya through the production of cowpea leaf soup mix. However, the adoption of these techniques has an economic perspective that guides decision-making. This study utilized a two-stage linear programming methodology using NutriSurvey and the analytic hierarchy process in a seven-step hierarchy for the production of a cowpea leaf soup mix of an optimal nutrition and sensory quality. The optimal inclusion level of cowpea leaves into the soup mix was 49%. With an R2 of 61.36%, consistency, taste, and mouthfeel were the greatest determinants of the acceptability of cowpea leaf soup mixes. The incorporation of blanching in solar drying and sun drying were the least costly options with priority vectors of 0.08 and 0.09 (CR < 0.1) respectively, whereas, in the use of mechanized processing techniques such as oven drying, priority vectors of 0.10–0.19 had higher maximum benefits than the local processing technique of sun-drying that had a priority vector of 0.08 (CR < 0.1). The benefit-cost ratio was maximal without extrusion, with the solar-drying pathway having the highest benefit-cost ratio of 1.5. The study found that resource-intensive pathways yielded maximum benefits in the retention of quality. However, with the exclusion of extrusion, the benefit-cost ratio of the processes improved.

Alternaria malorum, a new causal agent of cowpea leaf spot disease in Iran

Cowpea (Vigna unguiculata, Fabaceae) is an annual herbaceous legume cultivated for seed and fodder. During a survey in May 2022, cowpea leaves with leaf spot symptoms were collected from a field in which c. 40% of the plants were diseased (Karaj City, Alborz province, Iran). Leaf spots began as small circular water-soaked lesions at the leaf centre and margins which expanded and on occasion, coalesced. The infected tissue became pale brown and necrotic. Isolation of the causal pathogen was performed using the high humidity blotter method. After five days, growing fungi were transferred with a fine sterile needle to 2% water agar. Pure cultures were obtained using the hyphal tip method on synthetic nutrient-poor agar (SNA) and potato carrot agar culture media. Fungal colonies were incubated at 25°C with an 8 hour light/16 hour dark photoperiod for seven days. A typical colony (ALT1) reached 58 mm in diameter after seven days incubation on SNA culture medium. The colony was olive-brown to dark brown at the centre, with a white margin. Aerial mycelia were sparse. Mycelia were septate, pale brown and smooth–walled. Sporulation was abundant on SNA, mostly from the aerial hyphae. Conidiophores arose singly from the aerial mycelia, and were brown, erect, simple, short, smooth, frequently reduced to conidiogenous cells with a slight swelling at the apices, 7–30 × 3–5 μm. Conidiogenous loci were 1–3 per conidiogenous cell, and brown. Ramoconidia were 0–3 septate, ellipsoid to cylindrical, smooth, brown, 15–32 × 3–5 μm, with a short beak (n = 50). Conidia were subcylindrical, ellipsoid or fusiform, brown, smooth, in long acropetal chains, simple or with lateral branches and 8–11 × 3–3.5 μm (n = 50) (Figure 1). Morphological and cultural characteristics of the recovered isolate (ALT1) were similar to the description of Alternaria malorum provided by Goetz & Dugan (2006) and Crous et al. (2009). Molecular characterisation of isolate ALT1 was done by PCR amplification and sequencing of the internal transcribed spacer (ITS) region using the ITS1 and ITS4 primers (White et al., 1990). The obtained sequence was deposited in GenBank (Accession No. OP006224) and a BLAST search showed it had 100% identity to isolates of A. malorum (MW335156, LR134074, FJ839611 and KY077556). Maximum likelihood analysis was performed by heuristic search with Mega X software. In the generated phylogenetic tree (Figure 2), isolate ALT1 was separated from closely related Alternaria species and other fungal genera, and clustered in the same group as A. malorum isolates. The molecular analysis confirmed the morphological identification of the pathogen. Pathogenicity testing was performed by spraying a conidial suspension (106 conidia/ml) of isolate ALT1 on healthy and surface-sterilised cowpea leaves without wounding, and was replicated three times. Sterile water was sprayed on the leaves of control plants. All plants were covered with plastic bags to maintain high humidity and placed on a glasshouse bench at 25°C with a 12 hour photoperiod until the development of disease symptoms. Leaf spots appeared twelve days after inoculation (Figure 3) and resembled those observed in the field. The pathogen was re-isolated from the newly generated leaf spots, fulfilling Koch's postulates. In Iran, Alternaria malorum was first reported by Asgari et al. (2004) as Cladosporium malorum from the leaves of the Hordeum vulgare in East Azarbaijan province. Alternaria malorum has also been reported as a fungus associated with declining Persian oak trees (Alidadi et al., 2018). Bagherabadi & Zafari (2022) also reported A. malorum as the causal agent of bark canker in walnut trees. Several diseases are known to infect cowpea, including anthracnose, Cercospora leaf spot, damping off, Fusarium wilt, Sclerotium stem, root and crown rot, Septoria leaf spot, and scab (Dugje et al., 2009). This is the first report of Alternaria malorum as a causal agent of cowpea leaf spot disease in Iran and globally. We are thankful to the University of Tehran for supporting this research.

Cowpea leaf width correlates with above ground biomass across diverse environments

AbstractCowpea (Vigna unguiculata [L.] Walp.) yields within the dry savannahs of Sub‐Saharan Africa are low. Given the contribution of cowpea to food security in this region, it is essential that high‐yielding varieties are developed to improve crop productivity in a sustainable manner. Identifying morphological or physiological traits that correlate with biomass could assist breeders with rapid screening of diverse germplasm. This study investigated 23 diverse Nigerian cowpea lines in an environmentally controlled greenhouse and 50 diverse lines from a Multiparent Advanced Generation Intercross (MAGIC) population in the field to identify easily measurable traits associated with high above ground biomass. Correlation analyses found that leaf traits were significantly and positively correlated with above ground biomass, and the leaf width of the youngest fully expanded leaf was the best indicator of biomass yield. Analysis of variance identified significant differences among the genotypes for all measured traits, indicating that there is genetic variation among these varieties and opportunity for selection. These results from the greenhouse and the field indicate that the leaf width of the youngest fully expanded leaf can be used to rapidly select cowpea lines with high biomass production potential.

English

Reaching the second UN Sustainable Development Goal requires improving the nutritional value of food products and dietary diversity. Simultaneously, recent research highlights the importance of processing highly nutritious but underutilized African leafy vegetables (ALV) for lowering post-harvest losses and bridging off-season gaps. Combining both goals, it seems promising to utilize neglected ALV for enhancing conventional food items that are already well accepted in consumer diets but low in nutritional value. Therefore, this study analyzes consumer demand for maize (Zea mays L.) and millet (Eleusine coracana (L.) Gaertn) porridges combined with cowpea leaf powder (Vigna unguiculata L.Walp) (CLP) in Kayunga, Uganda. The study relies on combining sensory analysis with a binding Becker-DeGroot-Marschak auction to analyze consumer demand. Results show that consumer acceptance of CLP-enhanced porridges is predominantly shaped by sensory perception (p < 0.05). Although adding CLP lowers consumers’ sensory appreciation, the study still identifies a reasonably large group of consumers, nearly 50% of the participants, who valued CLP-enhanced porridges as much as plain ones. This justifies the conclusion that adding CLP is not without risks but is accepted among many consumers and can thus help to promote the consumption of locally available plants. For future product development, we recommend that priority is given to sensory attributes, and special focus is placed on consumers who barely incorporate fresh vegetables into their diets.   Key words: African leafy vegetables, Uganda, willingness to pay, sensory analysis, porridge.

Proximate composition and sensory characteristics of refractance window dried cowpea composite porridges

Undernutrition is a major public health concern in Uganda. Locally available nutrient dense diets can help reduce the problem of undernutrition. Utilisation of cowpea leaf powder in preparing composite porridge blends depends on sensory acceptance of the consumers. A Nutrisurvey software was used to formulate two composite flour blends, namely maize and millet in a ratio 2:8 and cowpea-maize in a ratio of 1:9 to achieve the daily requirement of protein for children. The study developed a process for the production of composite cowpea flour from finger millet flour and maize flour and followed a one factor design in which maize flour (MF) and millet flour (MMF) was substituted with cowpea leaves flour (CPL). The composites were dried using refractance window drying technology. The proximate composition of the composite flours were determined using standard methods while sensory acceptability of porridges was rated on a five-point Likert scale using an untrained panel. Results indicated a significant (p < 0.05) increase in protein (10.9 to 13.4%), dietary fibre (11.01 to 13.0%) and lipids (4.71 to 5.3%) contents for cowpea-millet composite porridge. For cowpea-maize composite flour, a significant (p < 0.05) increase in protein (5.9 to 7.6%), dietary fibre (1.47 to 3.3%) and lipids (2.84 to 3.3%) was also observed. Sensory evaluation indicated that between the two composite porridges, the cowpea-millet porridge blend was significantly (P≤0.05) more appealing in terms of colour (3.61±0.8), aroma (2.96±0.2), taste (3.24±0.6), texture (3.62±0.6) and general acceptability (3.61±0.8) to the panellists than the cowpea-maize porridge blend. The cowpea-millet and cowpea-maize composite flours can contribute more than 100% of the recommended dietary allowance of protein and carbohydrate requirements for children aged 0-8 years. The study findings indicate that the cowpea-based composite flours have the potential to make a significant contribution to the improvement in the nutritional status of infants and children in developing countries.

Identification and molecular characterisation of cercospora leaf spot disease pathogen on cowpea (Vigna unguiculata L. Walp)

Cercospora leaf spot disease (CLSD) is a serious constraint to the production of cowpea worldwide, especially in the tropics. This study was conducted to identify the causative agent of CLSD on cowpea accessions. Infected cowpea leaf samples were collected from established cowpea experimental field at the Institute of Agricultural Research and Training (IAR&T), Ibadan. The leaves were placed on potato dextrose agar (PDA) and sub-cultured to obtain pure fungi isolates. Nucleic acid extraction from the pure culture was carried out at the molecular laboratory of National Horticultural Research Institute (NIHORT), Ibadan. Polymerase chain reaction (PCR) was carried out to amplify fungi nucleic acid using ITS1 and ITS4 universal primers. The amplicon obtained were subjected to Basic Alignment Search Tool (BLAST) to determine the sequence homology. These sequences were compared with known sequences on the National Centre for Biotechnology Information (NCBI) database. The sequences analysed had similarity with Cercospora canescens (MK029364.1 and MW756382.1) deposited on the NCBI database. This study confirms that C. canescens is the causal pathogen of CLSD found on the infected cowpea leaves.

Effect of Pre-treatment and Processing on Nutritional Composition of Cassava Roots, Millet, and Cowpea Leaves Flours

Cassava roots, millet and cowpea leaves have short storage life thus the need for simple post-harvest handling and storage protocol to ensure prolonged availability to fully contribute toward food and nutrition security, a major challenge within Sub-Saharan Africa. The current study sought to investigate the effect of pre-treatment and processing on cyanide safety and nutrition composition of cassava roots, millet and cowpea leaves flours. The study used three popular cassava varieties grown along the Kenyan coast, cowpea leaves (M66) grown as vegetable and pearl millet. The study used analytical techniques as guided by AOAC standard methods, to determine the nutritional composition of the individual crops while subjecting them to pre-treatment processes (blanching, peeling, washing, drying, and fermentation) and optimizing for maximum nutrient composition. The cyanide content ranged 7.8–9.5, 3.4–5.0, and 2.2–2.8 ppb for raw, untreated, and fermented cassava flours, respectively. The carbohydrates content was in the range of 35–37, 81.73–83.49, and 70.28–71.20% for raw cowpea leaves, cassava roots, and millet, respectively; the carbohydrate content for untreated flours was in the range of 35.68–35.19, 66.07–83.49, and 66.07–68.89% for cowpea leaves, cassava roots, and millet, respectively; the carbohydrate content for the fermented flours was in the range of 29.06–28.01, 79.68–84.36, and 69.08–70.12% for cowpea leaves, cassava roots, and millet, respectively. The protein content was in the range of 25.69–26.01, 1.2–18, and 11.1–13.3% for untreated cowpea, cassava, and millet flours, respectively; fermented flours protein content was in the range of 25.7–29.3, 1.3–2.2, and 8.5–11.1% cowpea, cassava, and millet flours, respectively. Iron and zinc contents were in the range of 4.31–9.04, 1.0–1.3; 7.98–7.89, 1.21–1.25; 6.58–8.23, 0.99–1.22 (mg/100 g dwb) for raw, untreated, and fermented cowpea flours, respectively. Pre-treatment had significant effects (P ≤ 0.05) on cyanide content and nutritional composition of each of the flours. Farmers should be trained to utilize such simple processing techniques.

Exploiting Potential of Trichoderma harzianum and Glomus versiforme in Mitigating Cercospora Leaf Spot Disease and Improving Cowpea Growth.

Trichoderma species are of utmost importance in agro-biotechnological applications because, in their interactions with plant hosts, they out-compete most pathogenic microorganisms. This study aimed at exploiting the potential of Trichoderma harzianum together with Glomus versiforme and its mutants, in inhibiting cowpea leaf spot rot induced due to Cercospora canescens infestation and improving agronomic growth parameter in a screen house experiment. The experiment was designed using single and co-inoculation of the bioagents: in all, eleven treatments were applied, consisting of Glom_verwild, Glom_ver30, Glom_ver60, Glom_ver90, Trich_h, Glom_verwild+Trich_h, Glom_ver30+Trich_h, Glom_ver60+Trich_h, Glom_ver90+Trich_h, Pathogen alone and control. Cowpea growth yield parameters and disease severity were assessed after 7 weeks. The deployed treatments improved agronomic growth parameters substantially (p<0.05) relative to control. Glom_ver 60+Trich_h treatment exerted the highest agronomic growth improvement yield. In addition, the best reduction in the incidence and severity of cowpea leaf spot disease was obtained using Glom_ver 60+Trich_h. A significantly higher germination rate in seeding, confirms both inhibitory and growth improvement potency of the bio inoculants treatment. This study's findings confirmed the beneficial impacts of the treatment of seed and soil with dual T. harzianum and G. versiforme, in improving the immunity of cowpea to Cercospora canescens leaf spot infection and improve cowpea growth.

First Report of Nigrospora sphaerica associated with Leaf Spot Disease of Cowpea (Vigna unguiculata) from India.

Cowpea (Vigna unguiculata (L.) Walp) is one of the main legume crops grown in arid and semi-arid regions in the world. Brazil, Haiti, Myanmar, Nigeria, Sri Lanka, United States, and India contributes to the substantial production of cowpea at the global level (Mahadevakumar and Janardhana, 2012, 2014). Field surveys conducted during 2017-19 (August-September) in major cowpea growing regions of southern Karnataka revealed the occurrence of characteristic leaf spot disease of unknown etiology with an incidence ranging from 6 to 8%. Initially, the symptoms developed as small specks (1.5 to 3.5 mm), characterized by circular or irregular shape. These lesions began to develop from the leaf margin and regularly extended and coalesced to form larger lesions. After the successful manifestation of the symptoms on leaves, the associated fungal pathogen was isolated. In brief, the infected leaves were surface sterilized with 2% NaOCl for 2 min, rinsed thrice in sterile distilled water (SDW) and blotter dried. The leaf sections were placed on potato dextrose agar (PDA) in Petri plates and incubated at room temperature (27 ± 2°C) for 10 to 12 days. Mycelia developed from infected tissues were transferred to fresh PDA plates and pure cultures were obtained. Mycelia were initially white and eventually turned into gray. The conidia were black, single-celled, smooth, spherical to subspherical, 10 to 22 μm in diameter (n=30), and borne singly on a hyaline vesicle at the tip of each conidiophore. Based on the cultural features and conidial morphology, the fungus was identified as Nigrospora sp. Further, to identify the pathogen to the species level, the ITS region of the ribosomal RNA gene was amplified using primers ITS1 and ITS4 (White et al. 1990). The amplified PCR products were purified and sequenced. The nBLAST analysis showed 100% similarity with reference sequences from the GenBank database Nigrospora sphaerica (MT225783.1; MN795578.1), and the sequences were deposited in GenBank (Accession No. MT305812.1, MT305813.1, MT305814.1). Based on the cultural, morphological, microscopic and molecular characteristics, the associated fungal pathogen was identified as N. sphaerica (Sacc.) Mason (Chen et al. 2018; Wang et al. 2017) and a voucher specimen was deposited at University of Mysore Herbarium with accession No. UOM20-NS1. Further, pathogenicity tests were conducted on healthy cowpea plants grown under greenhouse conditions. Inoculations were made with conidial suspension (105 conidia/ml) prepared in SDW and healthy plants sprayed with SDW served as a standard control. All the plants were covered with polyethylene bags for 24-48 hr and observations were made at regular intervals. Typical necrotic lesions developed after 12 days of inoculation and no such symptoms were observed on the standard control set. The associated pathogen was re-isolated from diseased leaves and its identity confirmed based on morphology and cultural characteristics. Leaf spots are becoming a major problem in cowpea growing areas in recent years (Dactuliophora sp., Pestalotiopsis leaf spot, Alternaria leaf spot, and many others) (Mahadevakumar and Janardhana 2012, 2014). Recently, Aplosporella hesperidica causing collar rot on cowpea has been reported from the same region (Deepika et al. 2020). The seed borne occurrence N. sphaerica on cowpea is reported from Brazil (Rodrigues and Menezes 2002), there are no previous reports available on the occurrence of N. sphaerica on cowpea leaf spots, the present investigation is the first report of N. sphaerica causing leaf spot disease on cowpea from India.

English

Cowpea production is common among smallholder subsistence farmers of Western Kenya due to its wide ecological adaptation. However, this crop is affected by cowpea rust Uromyces phaseoli var vignae (Baarel) Arth disease, causing economic yield losses with limited control measures. This study therefore, evaluated cowpea rust disease incidence (DI) and severity (DS) on growth of selected improved cowpea genotypes. A Randomized Complete Block Design (RCBD) in split plot arrangement experiment was conducted in Busia and Kakamega counties, Kenya during short rains of 2018 and long rains of 2019. Cowpea genotype: K80, KVU 27-1, Tumaini, Dakawa and local variety was the main factor and cropping system: pure stand cowpea and cowpea intercropped with maize was the sub plot-factor. Data were subjected to Mixed model ANOVA using SAS. The DI and DS were 41 and 39% respectively less in Dakawa and Tumaini with more cowpea leaf and grain yields compared to other genotypes. On the other hand, DI and DS were 35 and 56% respectively less in pure stand cowpea compared to intercrop cowpea. Pure stand cowpea also had more leaf and grain yields. The results indicate that Dakawa and Tumaini cowpea genotypes have potential resistance to cowpea rust and the conditions could be improved by planting cowpea in pure stand. Key words: Cowpea genotype, cropping system, cowpea rust incidence, severity. &nbsp

Productivity and biological N2-fixation in cereal-cowpea intercropping systems in sub-Saharan Africa. A review

Intercropping is a common practice among farmers in sub-Saharan Africa, regarded as a sustainable way of improving land productivity to meet food and nutritional requirements for a growing population, especially in marginal areas. Cowpea (Vigna unguiculata L. Walp) is often intercropped with major cereal crops, maize (Zea mays L.), sorghum (Sorghum bicolor L. Moench) and pearl millet (Pennisetum glaucum L.R.Br ). Here we conducted a systematic literature review on cowpea intercropped with maize, sorghum or pearl millet reported in sub-Saharan Africa with the objectives (i) to determine yield and productivity of component crops and (ii) to quantify biological N2-fixation in sole or intercrops. We retrieved 60 unique publications combining 1196, 998 and 25 observations of yields, land productivity and N2-fixation, respectively, for crops grown as intercrops and monocrops. The major results are as follows: (1) land productivity of cowpea intercropped with maize, sorghum and pearl millet is favourable, with average land equivalent ratios of 1.42 ± 0.47, 1.26 ± 0.35 and 1.30 ± 0.32, respectively; (2) no significant differences between the proportion of nitrogen derived from the atmosphere (%Ndfa) for sole or intercropped cowpea were found, with average values of 56.00 ± 4.89 and 46.62 ± 7.05, respectively; (3) however, the total amount of fixed nitrogen was higher in cowpea monocropping systems due to higher biomass production; nitrogen fixation was 57 kg N ha−1 and 36 kg N ha−1 in monocrops and intercrops respectively. We conclude that cereal-cowpea intercropping is a pathway for intensification for the low nutrient input systems of smallholder farmers in sub-Saharan Africa. Our review also suggests potential for improvement of these systems, based on the choice of the associated varieties, planting patterns and sowing time, cowpea leaf harvesting as a vegetable, and fertilization.

A detached leaf assay for testing transient gene expression and gene editing in cowpea (Vigna unguiculata [L.] Walp.)

BackgroundThe legume cowpea (Vigna unguiculata L.) is extensively grown in sub-Saharan Africa. Cowpea, like many legumes has proved recalcitrant to plant transformation. A rapid transient leaf assay was developed for testing gene expression and editing constructs prior to stable cowpea transformation, to accelerate cowpea and legume crop improvement.ResultsAttempts to develop a transient protoplast system for cowpea were unsuccessful. Leaflets from plants 3–4 weeks post-germination were age selected to establish a rapid Agrobacterium (Agro) infiltration-mediated transient system for efficacy testing of gene expression and CRISPR/Cas9 gene editing constructs. In planta, Agro-infiltration of leaflets with fluorescent expression constructs, resulted in necrosis. By contrast, Agro-infiltration of detached leaflets with an Arabidopsis (At) ubiquitin3 promoter:ZsGreen construct, followed by culture on solid nutrient medium resulted in fluorescence in over 48% of leaf cells. Expression efficiency was leaf age-dependent. Three cowpea meiosis genes were identified for CRISPR/Cas9 gene-editing, with the forward aim of meiosis-knock out for asexual seed induction in cowpea. Constructs were designed and tested containing candidate gene-specific guide RNAs, expressed using either the cowpea or Arabidopsis U6 promoters with Cas9 expression directed by either the Arabidopsis 40S ribosomal protein or parsley ubiquitin4-2 promoters. Leaflets were infiltrated with test gene-editing constructs and analytical methods developed to identify gene-specific mutations. A construct that produced mutations predicted to induce functional knockout of in the VuSPO11-1 meiosis gene was tested for efficacy in primary transgenic cowpea plants using a previously established stable transformation protocol. Vuspo11-1 mutants were identified, that cytologically phenocopied spo11-1 mutants previously characterized in Arabidopsis, and rice. Importantly, a biallelic male and female sterile mutant was identified in primary transgenics, exhibiting the expected defects in 100% of examined male and female meiocytes.ConclusionThe transient, detached cowpea leaf assay, and supporting analytical methods developed, provide a rapid and reproducible means for testing gene expression constructs, and constructs for inducing mutagenesis in genes involved in both vegetative and reproductive developmental programs. The method and tested editing constructs and components have potential application for a range of crop legumes.

Potential of food-to-food fortification with cowpea leaves and orange-fleshed sweet potato, in combination with conventional fortification, to improve the cellular uptake of iron and zinc from ready-to-eat maize porridges.

An emerging tool in the fight against the high prevalence of micronutrient deficiencies in sub‐Saharan Africa is the production of nutritionally enhanced staple food products, through food‐to‐food fortification with micronutrient‐dense fruits and vegetables. This study investigated food‐to‐food fortification with cowpea leaves (CL) and orange‐fleshed sweet potato (OFSP) in combination with conventional micronutrient fortification and fermentation on the mineral and antinutrient contents and Caco‐2 cellular uptake of iron and zinc from ready‐to‐eat maize porridges. The amount of iron and zinc taken up from maize porridges (0.05 and 0.06 mg/100 g, db, respectively) was increased more after fortification with CL, compared to OFSP (0.32 and 0.23 mg/100 g, db versus. 0.11 and 0.04 mg/100 g, db, respectively). Despite the moderate cellular uptakes of iron and zinc from the CL fortified porridges (2.71% and 3.10%, respectively) compared to the OFSP fortified porridges (6.51% and 5.22%, respectively), the CL fortified porridges had much higher high iron and zinc contents (12.2–14.1 and 7.6–8.9 mg/100 g, db versus. 2.1–3.7 and 1.5–2.7 mg/100 g, db, respectively). This highlights the importance of increasing both the mineral content and bioavailability when fortifying a product. Even when a food product contains substantial antinutrients such as CL, if the mineral content and contents of bioavailability enhancers are high enough, the amounts of bioavailable iron and zinc can still be improved.

Bio-pesticide actions of aqueous extract of &lt;i&gt;Ocimum gratissimum&lt;/i&gt;, &lt;i&gt;Piper nigrum&lt;/i&gt;, &lt;i&gt;Xylopia aethiopica&lt;/i&gt;, &lt;i&gt;Azadirachta indica&lt;/i&gt; and &lt;i&gt;Zingiber officinale&lt;/i&gt; formulation on cowpea leaves

The emergence of widespread insecticide resistance and the potential environmental problems associated with synthetic pesticides have indicated more interest for bio-pesticide usage in pest control. This study investigates the efficacy of a bio-pesticide formulation based on the aqueous extract of five plants namely Ocimum gratissimum, Piper nigrum, Xylopia aethiopica, Azadirachta indica, and Zingiber officinale in reducing cowpea leaf damage in event of bean beetle attach. Cowpea seeds were sown in four (4) different pots containing loamy soil and kept separately in the field at a distance of 10meters. Seven 7 days after foliage production, pots 1 and 2 were treated with 250ml of the formulations daily for 7 days, while pot 3 and 4 were not treated. From observations, the treated Cowpea plants were not attacked by bean beetle, while the untreated Cowpea plants were attacked by bean beetle, causing great damage on the foliage and this can lead to wilting, chlorosis and other fungal and bacterial diseases. Synthetic pesticides used for pests control, have adverse effects on crops and environment, but bio-pesticides formulated in this research is environmentally friendly, target specific and biodegradable. The extracts showed significant effect at p&lt;0.05.Keywords: Bio-pesticide, Vigna unguiculata Protection, Insect, Wasteland Weed