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European Journal of Applied Sciences – Vol. 10, No. 2
Publication Date: April 25, 2022
DOI:10.14738/aivp.102.11786. Ritte, I. P., Egnin, M., Idehen, O., Mortley, D., Bernard, G. C., Binagwa, P. H., Brown, A. P., & Bonsi, C. K. (2022). Evaluation of Cowpea
Morpho-physiological and Yield Responses to Vegetative and Pre-Anthesis Water-Deficit Stress Tolerance under Greenhouse
Conditions. European Journal of Applied Sciences, 10(2). 391-411.
Services for Science and Education – United Kingdom
Evaluation of Cowpea Morpho-physiological and Yield Responses
to Vegetative and Pre-Anthesis Water-Deficit Stress Tolerance
under Greenhouse Conditions
Inocent P. Ritte
Department of Agriculture and Environmental Sciences
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
Marceline Egnin
Department of Agriculture and Environmental Sciences
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
Osagie Idehen
Department of Agriculture and Environmental Sciences
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
Desmond Mortley
Department of Agriculture and Environmental Sciences
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
Gregory C. Bernard
Department of Agriculture and Environmental Sciences
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
Papias H. Binagwa
Department of Agriculture and Environmental Sciences
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
Adrianne P. Brown
Department of Agriculture and Environmental Sciences
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392
European Journal of Applied Sciences (EJAS) Vol. 10, Issue 2, April-2022
Services for Science and Education – United Kingdom
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
Conrad K. Bonsi
Department of Agriculture and Environmental Sciences
Plant Biotech and Genomics Research Laboratory
College of Agriculture, Environment and Nutrition Sciences
Tuskegee University, Tuskegee, AL 36088, USA
ABSTRACT
Cowpea production is severely hindered by water scarcity; thus, understanding
morpho-physiological response mechanisms of known drought-tolerant cultivars
under water-deficit stress is critical to identify and establish representative yield- related traits of climate-hardy cowpeas. To determine cowpea genotypic variability
to drought-tolerance, seventeen days-post sowing (DPS) greenhouse plants were
subjected to 14-days drought stress without watering, then watered every 10-days
at 25%, 50%, and 75% field capacity (FC) until maturity in two-trial experiment.
Controls were well-watered at 100% FC every 3-days. Drought stress data were
collected on plant height, stem diameter, chlorophyll content and terminal leaflet
expansion rate. At maturity, 83 to 119 DPS, pod number, shoot and root biomass,
and seed yield per plant were recorded. Data were combined and analyzed using
analysis of variance. Drought tolerance was evaluated by percent change in
performance and stress tolerance indexes. Drought stress in both trials impacted
phenotypic expression. Plant height declined by 74%, stem diameter 18.2%,
chlorophyll content, 47.6% terminal leaf length 83.2%, and width 85.2%. Pods per
plant were reduced by 73% and seed yield by 98.8%. The estimated correlation
between morpho-physiological and other yield-related traits of drought-tolerance
indices verified that TVu 11987, LOBIA-I-SEFADE, and TVu 7362 were drought
tolerant along with confirmed tolerant commercial cultivars California Blackeye
No.5, Big Boy, and Lady. These cultivars exhibited different stress-coping strategies
of low water requirements and growth performance to yield reduction. Overall, the
genotypic performance recorded as drought-tolerant characteristics may be
recommended as potential screening factors for donor cultivar traits in cowpea
breeding programs.
Keywords: Cowpea (Vigna unguiculata), Water Stress, Field Capacity, Morpho- physiological Traits, Growth and Grain Yield Response.
INTRODUCTION
Cowpea [Vigna unguiculata (L.) Walp.], Fabaceae, (2n = 2x = 22) is an important legume and
inexpensive source of protein, vitamins, minerals and fiber for millions of low-income
households where it is consumed as dry grain and leaves as vegetables [1], [2]. According to
Food and Agriculture Organization (FAO), 14.5 million ha of land are devoted to cowpea
production, mainly in the African countries of Niger, Nigeria, Burkina Faso, Mali, and Sudan,
accounting for 75% of global grain production and 78% of cultivated area. However, the
average production in most African countries is below 1t ha-1 compared to the potential yield
of up to 3t ha-1 [3], [4] due to abiotic factors such as environmental fluctuations and soil and
water limiting conditions. These factors are important plant growth and development
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Ritte, I. P., Egnin, M., Idehen, O., Mortley, D., Bernard, G. C., Binagwa, P. H., Brown, A. P., & Bonsi, C. K. (2022). Evaluation of Cowpea Morpho- physiological and Yield Responses to Vegetative and Pre-Anthesis Water-Deficit Stress Tolerance under Greenhouse Conditions. European Journal
of Applied Sciences, 10(2). 391-411.
URL: http://dx.doi.org/10.14738/aivp.102.11786
determinants, particularly drought, which can severely limit the productivity and quality of
cowpeas. In the United States (U.S.), cowpea is an introduced field, and horticultural crop with
much of the production predominantly practiced in the southern states where cowpea remains
a staple food [4], [5], [6]. Cowpea production in the U.S. is practiced on about 5,220 ha in which
11,750 tons of cowpeas are harvested [3], [7] as dried seed commonly known as black-eyed
peas or southern peas, and often cooked, canned or frozen. Furthermore, some cowpeas are
harvested while the seeds are high in moisture, and sold fresh [4], [8], [9]. The U.S dry cowpea
production has been continuously declining due to changing cropping systems, environmental
fluctuations and overall food consumption trends as opposed to increased land devoted for
cowpea production in other regions [4], [9]. Other sources suggests that, the collapse of cowpea
acreage is associated with increased acreage of soybean due to ease of mechanization and
reduced pest problems [10]. However, cowpea is considered more drought-tolerant than
soybeans and well adapted to sandy soil types [11].Due to the importance of cowpea
worldwide, versatile end uses and unique grain characteristics, there is a dire need to
understand its tolerance performance under soil water deficit and extreme temperatures to
help develop hardy crops with higher grain yield stability and better stress adaptation to
changes in the global climate.
As global climate change and related problems increase, water shortage is becoming
increasingly alarming [12]. These environmental constraints not only impact plant growth,
yield, and water relations, but also membrane integrity, pigment content, and photosynthesis
[13], [14], especially during pre-anthesis. Cowpea production, especially in Africa, is primarily
grown under rainfed conditions thus, its productivity is essentially hindered by erratic rainfall
patterns which either come late, at the beginning of the season or stops earlier than usual,
leading to severe drought conditions during the growing season [15], [16]. Although cowpea
species are naturally well-adapted to growing in drier regions where other legumes do not
perform well, many varieties are potentially affected by various environmental factors
resulting in a serious reduction of crop yield and quality [17], [18]. Hence, the adaptability of
some cultivars to withstand both heat and drought is of significant interest for gaining insight
into their resiliency in extreme environmental conditions.
Cowpea exhibits inherent genotypic variations in response to drought stress. Some cultivars
are comprised of discrete physiological and morphological traits that enhance their ability to
adapt to different environmental conditions [19]. Purushothaman et al., [20] indicated that root
traits like thick cortex aid cowpea to effectively absorb re-introduced soil moisture after
drought stress which enhances recovery. The application of efficient screening techniques
would facilitate the identification of key traits for breeding to improve drought stress
adaptation, yield, and quality. Phenotypic evaluation is the first step in the screening of
desirable and promising cowpea genotypes with drought adaptive characteristics [21], [22].
Two methods employed include the empirical or performance approach that uses grain yield
and its components as the main criteria, since yield is the integrated expression of the entire
array of traits related to productivity under stress. The second method is the physiological
approach that identifies a specific physiological or morphological trait that significantly
contributes to growth and yield in the event of drought [23]. Physiological parameters like
water potential, relative turgidity, diffusion pressure deficit, chlorophyll stability index and
carbon isotope determination are technically difficult and are associated with a high cost of
time and investment, especially when large numbers of breeding populations are involved [24],