Drought Tolerance In Cowpea Research Articles

Predictive Analytics in Genetic Engineering as an Optimization Problem

In genetic engineering, developing a breed with a desired trait is a search and optimization problem that sometimes requires many generations of field and laboratory experiments for an optimal solution to be found. The nature of the problem requires that a stochastic optimization algorithm be applied in the metaheuristic search rather than using a deterministic or mathematical approach. In the search for drought-tolerant cowpea, this study applied a genetic algorithm as a predictive analytics tool in the genetic engineering of three native cowpea landraces (Dan muzakkari, Gidigiwa, and Dan mesera) selected from Northern Nigeria (specifically from Kontagora in Niger State of Nigeria). The three cowpea species were subjected to mutagenic treatments using gamma irradiation and Ethyl Methane Sulphonate (EMS). Doses applied include 200, 400, 600, and 800 Gray of gamma irradiation and 0.372% v/v of EMS. Both treated and untreated cowpea landraces were planted and observed. Mutation-induced breeding aims to deepen the drought-tolerant trait of the cowpea mutants to survive conditions in drought-prone Northern Nigeria. The statistical analysis of the agro-morphological and yield parameters of the first mutant generation (M1 generation) indicates that mutagenic treatments have a positive impact on both the yield and the survival of the three landraces as all the treated landraces yielded better than the control, particularly the treatments combination of 600gray and 372% v/v of EMS. Also, the predictive outcomes of the computational simulation that was implemented in Python programming indicate that these local cultivars are developing drought-tolerant genetic variability. For the three computational experiments, the stochastic optimizer (genetic algorithm) converged at the 9412th, 9717th, and 14338th generations respectively. Such predictive analytics information is useful for guiding decision-making by researchers and breeders in the crop improvement program.

Elucidating the genomic regions through genome-wide association study (GWAS) for root traits in cowpea (Vigna unguiculata (L) Walp) mini-core collection

Enhancing the root traits through selection and breeding efforts can significantly improve the acquisition of soil resources, consequently boosting crop production in marginal environments. Cowpea is one of the important legume crops in arid and semi-arid regions, grown mostly in marginal environments under drought conditions. The roots play a crucial role in plant's ability to survive and adapt under such water stressed conditions. The understanding of cowpea genetic architecture related to root system architecture (RSA) remains limited due to difficulties in accurately measuring root traits. In the present study, a set 110 diverse mini-core collection of cowpea from IITA, Nigeria was evaluated for thirteen (13) different root-shoot traits under controlled conditions in the green house. Significant variation was recorded for all the root traits in the mini-core set. Most promising genotype for most of the root traits, viz., root volume, dry root weight, root biomass density and tap root diameter were identified. The correlation analysis revealed significant positive association (p < 0.001) of root weight with shoot weight (0.85), root volume (r = 0.61), and tap root diameter (0.56). In the principal component analysis (PCA), first three principal components explained the variance of 64.31%, with PC1 contributing 44.43%, PC2 10% and PC3 9.88%. All the root-shoot traits contribute positive variation to PC1especially dry root weight and dry shoot weight that had high component loading and in PC2 root shoot ratio had high loading. The root-shoot trait data was used with 6,574 good quality SNP data for discovery of genes/QTLs/marker-trait associations for root traits. The analysis of results of genome wide association study (GWAS) led to the identification of 52 unique SNPs associated significantly (p < 10−4) with thirteen root-shoot traits. Highest number of SNPs was found associated with root weight and chromosome 5 was identified as SNP hotspot for harboring majority of significant SNPs. We further delve candidate genes within 50 kb around the identified SNP that led to the identification of several important candidate genes underlying genomic regions responsible for root-shoot traits in cowpea. The promising cowpea genotypes for root traits and promising MTAs/candidate genes will prove useful in cowpea improvement programs including improvement of drought tolerance in cowpea.

Pre-sowing Seed Treatment with Proline, Glycine Betaine, and Soil Amendment with Compost as Strategies for Improving Yield and Drought Tolerance in Cowpea

Pre-sowing Seed Treatment with Proline, Glycine Betaine, and Soil Amendment with Compost as Strategies for Improving Yield and Drought Tolerance in Cowpea

Screening for drought tolerance in cowpea at the flowering stage

Drought is one of the major threats to cowpea productivity in tropical countries, and understanding its impacts is germane in ensuring food security in a global context. The present study was established to screen some accessions of cowpea for drought tolerance at the flowering stage in pots under the controlled conditions of a screen house. High significant differences were observed among accessions for wilting and recovery traits, stomatal conductance, relative water content (RWC), terminal leaflet length (TLL) and width (TLW), stem girth, and yield parameters under drought stress. In addition, drought stress caused a significant reduction in morphological traits and RWC between the initial and the final values. Based on cluster and Principal Component Analysis (PCA), accessions were separated into different classes of tolerance. Direct selection for wilting traits, stomatal conductance, morphological traits, and recovery parameters showing high heritability (≥ 60%), GAM (≥ 20%), and PCA (≥ 0.4) will be effective. Hence, four major classes of tolerance were determined: AC03, AC08, and AC10 were highly susceptible. AC01 and AC04 were moderately susceptible. AC06, AC07, and AC09 were moderately tolerant, while AC02 and AC05 were the highly tolerant accessions. The moderately tolerant and the highly tolerant accessions showed a combination of superior resistance to wilting, superior recovery rates, and superior yield attributes. They also showed lower stomatal conductance, higher RWC, and low reduction of RWC, TLW, and stem girth under drought stress compared to the susceptible ones.

Genotype by environment interaction and grain yield stability of drought tolerant cowpea landraces in Ethiopia

Genotype by environment interaction and grain yield stability of drought tolerant cowpea landraces in Ethiopia

Comparative analysis of aquaporins and its relationship with drought tolerance in cowpea and adzuki bean organs

Comparative analysis of aquaporins and its relationship with drought tolerance in cowpea and adzuki bean organs

Integrative small RNA and transcriptome analysis provides insight into key role of miR408 towards drought tolerance response in cowpea

Drought stress response studies and overexpression of vun-miR408 proved it to be essential for abiotic stress tolerance in cowpea. Small RNA and transcriptome sequencing of an elite high-yielding drought-tolerant Indian cowpea cultivar, Pusa Komal revealed a differential expression of 198 highly conserved, 21 legume-specific, 14 less-conserved, and 10 novel drought-responsive microRNAs (miRNAs) along with 3391 (up-regulated) and 3799 (down-regulated) genes, respectively, in the leaf and root libraries. Among the differentially expressed miRNAs, vun-miR408-3p, showed an up-regulation of 3.53-log2-fold change under drought stress. Furthermore, laccase 12 (LAC 12) was identified as the potential target of vun-miR408-3p using 5' RNA ligase-mediated rapid amplification of cDNA ends. The stable transgenic cowpea lines overexpressing artificial vun-miR408-3p (OX-amiR408) displayed enhanced drought and salinity tolerance as compared to the wild-type plants. An average increase of 30.17% in chlorophyll, 26.57% in proline, and 27.62% in relative water content along with lesser cellular H2O2 level was observed in the transgenic lines in comparison with the wild-type plants under drought stress. Additionally, the scanning electron microscopic study revealed a decrease in the stomatal aperture and an increase in the trichome density in the transgenic lines. The expression levels of laccase 3 and laccase 12, the potential targets of miR408, related to lipid catabolic processes showed a significant reduction in the wild-type plants under drought stress and the transgenic lines, indicating the regulation of lignin content as a plausibly essential trait related to the drought tolerance in cowpea. Taken together, this study primarily focused on identification of drought-responsive miRNAs and genes in cowpea, and functional validation of role of miR408 towards drought stress response in cowpea.

Insight into the cellular and physiological regulatory modulations of Class-I TCP9 to enhance drought and salinity stress tolerance in cowpea.

The Teosinte branched 1/Cycloidea/Proliferating cell factor (TCP) transcription factors are potent growth and developmental regulators in plants, also responsive to various hormonal and environmental stimuli. In this study, we primarily focused on the functional role of TCP9, a nuclear-localised Class-I TCP transcription factor in a drought and heat-tolerant legume crop, cowpea (Vigna unguiculata). Under drought stress, a higher protein expression level of TCP9 was observed in the leaves of the drought-tolerant cowpea cultivar Pusa Komal as compared to the drought-sensitive cultivar TVu-7778. Further, overexpression of VuTCP9 resulted in reduced cell and stomata size, aperture length and width while cell and overall stomatal density in the 35S::VuTCP9 transgenic cowpea lines increased. Phenotypic alterations, such as reduced leaf size and vigour, altered seed coats displaying extension pattern similar to the 'Watson pattern' and delayed senescence were prominent in the transgenic lines. Under normal conditions, the gas exchange and fluorescence measurements indicated reduction in transpiration rate (E), stomatal conductance (gs ) and photosynthetic efficiency (Φ PSII). However, water usage efficiency (WUE) remained unaltered in the transgenic lines as compared to the wild-type (WT) plants. Furthermore, the transgenic lines displayed higher tolerance to oxidative, drought and salinity stress, maintained relatively higher relative water content and lower occurrence of H2 O2 , as compared to the WT plants. Genes related to the jasmonic acid biosynthesis, stomatal development and abiotic stress responsiveness, such as TTG1, NAC25, SPCH and GRP1, increased and LOX2 decreased significantly in the transgenic lines.

Morpho-agronomic Characters Under Drought Stress and Genetic Diversity on the Local Landraces of Cowpea [Vigna unguiculata (L.) Walp] From East Nusa Tenggara Province, Indonesia

This study was performed to reveal the morpho-agronomic characters under drought and genetic diversity using SRAP (Sequence-related amplified polymorphism) marker on local landraces of cowpea (Vigna unguiculata (L). Walp) collected from East Nusa Tenggara Province, Indonesia. Data on drought response indexes according to the dry matter production of cowpea plants classified Carolina and Pinu Pahar as drought-sensitive and drought-tolerant cowpea genotypes, respectively. The assessment of the genetic diversity of cowpea genotypes was performed by using 25 SRAP combination primers. A total of 250 bands were produced by which 245 bands (98%) were polymorphic. The value of PIC (Polymorphic Information Content) of SRAP primers in this study varied from the highest value (0.97) to the lowest value (0.71) generated by primer pairs Me4-Em1 and Me3-Em4, respectively, with an average of PIC 0.87. An unweighted pair group method based on arithmetic averages (UPGMA) in this study was performed according to Nei and Li’s similarity index. The analysis of UPGMA and PCoA successfully separated Carolina and Pinu Pahar genotypes into different clusters. The result of the Mantel test showed that there was no significant correlation between the independent morpho-agronomic analysis and SRAP molecular matrix data.

Loci discovery, network-guided approach, and genomic prediction for drought tolerance index in a multi-parent advanced generation intercross (MAGIC) cowpea population

Cowpea is a nutrient-dense legume that significantly contributes to the population’s diet in sub-Saharan Africa and other regions of the world. Improving cowpea cultivars to be more resilient to abiotic stress such as drought would be of great importance. The use of a multi-parent advanced generation intercross (MAGIC) population has been shown to be efficient in increasing the frequency of rare alleles that could be associated with important agricultural traits. In addition, drought tolerance index has been reported to be a reliable parameter for assessing crop tolerance to water-deficit conditions. Therefore, the objectives of this study were to evaluate the drought tolerance index for plant growth habit, plant maturity, flowering time, 100-seed weight, and grain yield in a MAGIC cowpea population, to conduct genome-wide association study (GWAS) and identify single nucleotide polymorphism (SNP) markers associated with the drought tolerance indices, to investigate the potential relationship existing between the significant loci associated with the drought tolerance indices, and to conduct genomic selection (GS). These analyses were performed using the existing phenotypic and genotypic data published for the MAGIC population which consisted of 305 F8 recombinant inbred lines (RILs) developed at University of California, Riverside. The results indicated that: (1) large variation in drought tolerance indices existed among the cowpea genotypes, (2) a total of 14, 18, 5, 5, and 35 SNPs were associated with plant growth habit change due to drought stress, and drought tolerance indices for maturity, flowering time, 100-seed weight, and grain yield, respectively, (3) the network-guided approach revealed clear interactions between the loci associated with the drought tolerance traits, and (4) the GS accuracy varied from low to moderate. These results could be applied to improve drought tolerance in cowpea through marker-assisted selection (MAS) and genomic selection (GS). To the best of our knowledge, this is the first report on marker loci associated with drought tolerance indices in cowpea.

Integration of Seed Priming and Biochar Application Improves Drought Tolerance in Cowpea

Cowpea is a highly nutritious grain legume crop, cultivated mostly in a semi-arid environment and frequently confronts sporadic dry periods during different stages of plant growth, which drastically reduce its productivity. The current study was enacted to evaluate the biochar application and seed priming induced drought tolerance in cowpea. The seeds of cowpea were primed with CaCl2 (1% solution), water (hydropriming) (positive control), and dry seeds (absolute control), sown in pots with and without mango wood biochar. The water holding capacity (WHC) in well-watered and drought-stressed pots was maintained at 70% and 35%, respectively. Drought stress caused a delay in germination and reduced plant growth. Osmopriming enhanced seed germination, seedling growth, dry biomass production, chlorophyll contents, leaf area, soluble sugar contents, CO2 assimilation, water use efficiency (WUE), and leaf K+ concentration and inhibited the oxidative damage in cowpea under drought. The addition of biochar was effectively recuperated by the drought-induced growth reduction in cowpea. Osmopriming + biochar application increased the biomass production (115%), α-amylase activity (81%), chlorophyll contents (76%), total soluble sugars (60%), WUE (95%), leaf osmotic potential (25%), and leaf sap K + concentration (25%), and decreased the MDA content and total antioxidant activity by 34 and 28%, respectively, than non-primed control without biochar application under drought. Osmopriming supplemented with biochar amendment augmented the performance of cowpea under normal and water-deficit conditions through synchronized seedling emergence and better growth, chlorophyll synthesis, CO2 assimilation, osmolyte accumulation, and nutrient uptake with minimal oxidative damage, which lead to better cowpea performance in drought stress condition. Osmopriming and biochar application may prove effective in improving cowpea performance under changing climate.

Root and Agro-Morphological Traits Performance in Cowpea under Drought Stress

Drought is responsible for major yield losses in many worldwide crops and is expected to occur more frequently due to climate change. Cowpea, one of the most drought tolerant legumes, stands as a promising crop in the future climatic context. The screening for genotypes well adapted to this constraint is an essential step to improve cowpea production. A collection of 29 cowpea genotypes (Vigna unguiculata L. Walp.) from the Iberian Peninsula and 11 other countries from worldwide regions was grown and submitted to drought stress using pipes with 30 cm (control) and 90 cm (stress) of height in which water was supplied through the bottom. A set of root and agro-morphological parameters were evaluated, including shoot and root dry weight, root:shoot ratio and stem greenness. Overall, results show that under drought stress, plants seem to invest in root development and reduce shoot biomass. Higher root dry weight under drought conditions could be related to a higher drought tolerance in cowpea. Based on the evaluated traits, it was possible to identify genotypes, particularly C47 (Iran), C56 and C11 (Portugal), which might represent promising cowpea genetic resources for improved drought tolerance breeding.

Assessment of Cowpea (Vigna unguiculata (L.) Walp.) Mutant Lines for Drought Tolerance

Cowpea provides the cheapest source of protein with an average range of protein content of 23–30%. However, cowpea growth, development, and yield are greatly affected by drought during flowering and pod filling in the sub-Sahelian areas. The best way to cope with this situation is to develop drought-tolerant cowpea varieties. The objective of this study was therefore to evaluate cowpea lines developed through mutagenesis using gamma radiation to assess their reaction under optimal and water-stressed conditions. The response of ten mutants-irradiated Moussa local was then evaluated in pots arranged in a split plot design in a screen house. Two conditions were applied with optimum and water-stressed conditions. The stress was applied for two weeks at flowering. Two cowpea varieties Gorom local (drought-tolerant) and Moussa local (susceptible) nonirradiated were used as checks. Thereafter, field trials under two different sowing dates were conducted to identify the best tolerant mutant line(s) using agromorphological and tolerance indicators. The results indicated that mutant lines (MoussaM51-4P10 and MoussaM43-20P14) exhibited better stress tolerance and produced higher yield under water stress conditions. Stress Tolerance Index (STI) was better to select cowpea mutant tolerant with higher yielding under moderate stress (SI = 35%). The study confirmed that water stress has a negative effect on cowpea seeds production and on leaf chlorophyll content. The high temperature during experiment increased water stress effect mainly on non-irradiated checks (Gorom local and Moussa local).

GT biplot analysis of shoot traits indicating drought tolerance in cowpea [Vigna unguiculata (L.) Walp] accessions at vegetative stage

GT biplot analysis of shoot traits indicating drought tolerance in cowpea [Vigna unguiculata (L.) Walp] accessions at vegetative stage

Evaluation of cowpea for drought tolerance at seedling stage

Cowpea is a health-promoting diploid legume species [Vigna unguiculata (L.) Walp., 2n = 2x = 22]. The annual cowpea production is 5.4 million tons of dry seed globally. Despite the fact that cowpea is one of the most drought-tolerant crops, some genotypes with excellent agronomic traits such as high yield under sufficient water supplies have been reported to be highly drought-susceptible, thus still requiring the need for breeding drought-tolerant cowpea genotypes. Therefore, the objectives of this study were to evaluate drought tolerance in cowpea at seedling stage and to identify drought-tolerant cowpea genotypes. In this study, a total of 331 cowpea genotypes were evaluated for drought tolerance at seedling stage. The experiment was conducted in a greenhouse and repeated 3 times. Drought tolerance phenotyping was conducted using a previously described methodology and a total of 11 traits were analyzed. The experiment was validated by the use of drought-tolerant and susceptible controls. Results showed that: (1) a large variation in the evaluated traits for drought tolerance was identified among the 331 cowpea genotypes, (2) a high correlation was found for traits such as plant greenness score and tolerance to trifoliate leaf chlorosis under drought stress (r = 0.8), whereas no linear correlation was found for traits such as tolerance to trifoliate leaf chlorosis and unifoliate leaf SPAD chlorophyll under non-drought stress (r = 0.0), (3) a total of 21 genotypes were found to be drought-tolerant across different traits, and (4) country of origins could impact drought tolerance in cowpea. The top performing genotypes were repeated using an independent experiment to further validate the data. The results from this study would be of interest in breeding programs aiming at improving drought tolerance in cowpea.

Drought response of cowpea (Vigna unguiculata (L.) Walp.) landraces at leaf physiological and metabolite profile levels

Drought threatens the world’s food production, particularly in Sub Saharan Africa low external input and rain fed agricultural systems, where cowpea (Vigna unguiculata (L.) Walp.) is an important food crop. In the context of growing concerns regarding climate changes implications on water availability, this study aimed at 1) to evaluate the drought responses in cowpea landraces with contrasting drought tolerance levels (A55 – high sensitivity; A80 - mild sensitivity; A116 - tolerant), 2) using an integrated physiological (leaf gas exchanges; chlorophyll a fluorescence) and biochemical (photoprotective pigments; RuBisCO activity; primary metabolite profiling) analysis to identify drought tolerance probes, in plants submitted to three water availability levels (well-watered, WW; mild drought, MD; severe drought, SD). A116 plants maintained a better water status under drought, what could justify the higher Pn and Pnmax values in MD, as well as higher photochemical use of energy (reflected in the photochemical quenching (qL) and in the quantum yield of non-cyclic electron transport (Y(II))), and the lower need of photoprotective thermal dissipation mechanisms (given by the non-photochemical quenching (qN), and the quantum yield of regulated energy dissipation at photosystem PSII (Y(NPQ))), in MD and SD plants. Greater declines of net (Pn) and potential (Pnmax) photosynthesis were observed in A55 plants, which frequently showed significant impacts already under MD conditions in most parameters, whereas A80 usually displayed and intermediate behaviour. Still, even A55 showed some acclimation response, regarding photoprotective mechanisms associated with high contents of zeaxanthin, lutein, and carotenes, and high Y(NPQ), and qN values, supporting the absence of an increase in the non-regulated energy dissipation at PSII (Y(NO) did not increased) even in SD plants. Additionally, A55 was not significantly affected in RuBisCO activity, which showed to be quite resilient in cowpea. A primary metabolite profiling, complemented with a partial least square discrimination analysis (PLS-DA), allowed a better separation of A116 and A55 plants according to their degree of drought tolerance. In response to drought, A116 showed the greatest accumulation of most responsive metabolites, 14 in total, with sucrose, fucose, urea, alanine and putrescine being exclusively increased in this genotype, suggesting that they can be candidates as drought tolerance proxies. Other compounds, as proline, valine, isoleucine (among amino acids), and rhamnose and raffinose (among sugars) showed close increase patterns across landraces, thus they would be involved in the common drought response of cowpea plants. This pioneer approach to characterize Africa’s and Central Mozambique highly diverse cowpea germplasm, highlights the advantages of an integrated physiological and biochemical analysis, to identify response mechanisms and potential probes for drought tolerance in cowpea, aiming at to support selection and breeding strategies to obtain high yield and drought tolerant elite varieties.

Breeding and genetic management of drought in cowpea: Progress and technologies

Cowpea [Vigna unguiculata (L.) Walp] is one of the most important leguminous crops grown in tropics and sub-tropics worldwide. It serves as a good source of proteins and minerals for nutritional benefits of both humans and animals. However, its production is hindered by recurrent drought conditions associated with climate changes. Under abnormal conditions, drought alone causes grain and fodder yield losses of about 62% and 56% of realizable yield, respectively in cowpea. Numerous efforts to mitigate drought through breeding resilient cultivars are underway in many countries. Progress is hampered due to the fact that drought is a complex trait controlled by many genes that is affected by the environment. Consequently, breeding for drought tolerance requires an integration of various knowledge systems and methodologies from multiple plant science disciplines. The success of drought tolerance depends on the accumulation of additive genes, accurate control of stress environments and the use of high throughput selection methods to maximise selection gains. This review aimed at providing perspectives on the status of the progress made thus far on cowpea drought tolerance improvement and the technologies used for genetic management of drought tolerance in cowpea in order to reduce losses incurred due to moisture stress.

Genetic Variability for Flowering Time, Maturity and Drought Tolerance in Cowpea [Vigna unguiculata (L.) Walp.]: A Review Paper

Background: Cowpea plays a critical role in the lives of millions of people in Africa and other parts of the developing world, where it is a major source of dietary protein that nutritionally complements staple low-protein cereal and tuber crops. It is a valuable and dependable commodity that produces income for farmers and traders. Objective: To review related research work on the genetic variability for time to flowering, maturity and drought tolerance in cowpea.&#x0D; Data Source: Searches were made from the following databases and archives; International Institute of Tropical Agriculture (IITA), The Essential Electronic Agricultural Library (TEAL), Access to Global Online Research in Agriculture (AGORA) (FAO), AGRICOLA (National Agricultural Library), AGRIS - Agricultural Sciences and Technology (FAO), CAS - Chemical Abstracts (ACS), DOAJ - Directory of Open Access Journals, CABI, Euphytica, Elsevier, Research Alert, Scopus and CGIAR, Plant Genetics and Breeding Database, Crop Science Database, Plant Genetics and Breeding Database, data base repositories, using the terms “genetic variability”, “drought”, “tolerance”, “ time to flowering and maturity”, and “cowpea” individually or in combination to identify literature published in English language between January 1990 to January 2018.&#x0D; Methods: The review was carried out using the above search terms. Research papers were critically reviewed, relevant data extracted, and a narrative synthesis was conducted to determine the relevant papers.&#x0D; Results: In all 150 papers met the inclusion criteria. Collections were from varied background; Sub-Saharan Africa, Asia, Europe, and Latin Americas.&#x0D; Conclusion: Despite research studies on cowpea and drought, there appears to be limited such research findings on the time to flowering, and maturity in relations to drought tolerance in cowpea in Ghana, suggesting more research in this part of the world.

English

The use of multiple traits for drought study affirms the complexity of drought tolerance in cowpea. Despite the availability of several traits for drought tolerance evaluation, the rapid screening technique used by many scientists for seedling drought in wooden boxes is the simplest method for screening large populations. The objective of this study was to select drought tolerant cowpea recombinant lines developed from a drought tolerant and susceptible parent using the wooden box screening technique. Two hundred Recombinant Inbred Lines (RILS) an F2:6 generation were used for the study. The parents were drought tolerant line crossed with susceptible line. Screening was done in wooden boxes and plants stressed for 4 weeks and in two sessions. Leaf wilting, relative water content, chlorophyll content during stress, and recovery from drought data were taken. Results from this study showed significant differences (p &lt; 0.05) for relative chlorophyll content for the 4 weeks of water stress and relative water content taken on the second week of water stress for all 200 inbred lines, but no significant differences were observed for the parental checks. Relative water contents taken for RILS during water-stress ranged between 70-20% for drought tolerant and drought susceptible lines respectively. The parental lines used as checks both had relative water contents of 60%. Relative water content for the second experiment ranged between 74-22% for tolerant and susceptible RILS respectively. About 12 inbred lines consistently performed well for recovery, 13 RILS were susceptible. RILS that maintained a higher relative water and chlorophyll contents, with high proportion of survived seedlings were 11. Potential seedling drought tolerant RILS have been identified. Key words:&nbsp; Cowpea, leaf wilting, chlorophyll, recombinant inbred lines, drought tolerance, relative water content. &nbsp

Evaluation of diverse cowpea [Vigna unguiculata (L.) Walp.] germplasm accessions for drought tolerance

The genetic potential for drought tolerance in cowpea within the small holder sector has not been fully exploited in South Africa. Thus, a drought evaluation experiment was conducted at the ARC-VOP to evaluate 28 cowpea germplasm accessions including two controls viz. IT96D-602 (drought tolerant) and TVU7778 (susceptible to drought) in the drought screening house using plastic box evaluation method in January, 2017. Genotypes raised for three weeks were subjected to 5 weeks of water stress treatment to determine their physiological response through leaf wilting index, relative water content and proline content followed by re-watering to determine genotype (s) with ability to recover from drought stress. Analyses of variance showed highly significant differences in response to moisture stress among the cowpea accessions for the selected physiological traits except for leaf wilting index at week two of drought stress. Stem greenness and recovery appeared to be a reliable indicator of drought tolerant genotypes which was readily observed in Acc1257, Acc1168, Acc2355, IT96D-602 and Acc5352 which also correlated significantly and positively with relative water content and proline content. The genotypes responded differently to drought stress indicating that there is sufficient genetic variability that can be utilized further in breeding for drought stress within the cowpea species.