Identification of Novel Drought-tolerant Cowpea (Vigna unguiculata L.) Accessions through Field Evaluation under Drought Stress
J. N. Simbauni
Department of Plant Sciences, Chuka University, P. O. Box 109-60400, Chuka, Kenya.
D. K. Isutsa
*
Department of Horticulture, Egerton University, P. O. Box 536-20115, Egerton, Kenya.
M. M. Muraya
Department of Plant Sciences, Chuka University, P. O. Box 109-60400, Chuka, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Cowpea [Vigna unguiculata (L.) Walp.] has substantial nutritional and economic value, although leaf and grain productivity in Kenya remain low because of environmental stresses, including drought. This study aimed to identify high-yielding cowpea accessions under drought stress for use in developing drought-tolerant cultivars. Sixty cowpea accessions were evaluated for their responses to drought stress in two field trials arranged in a randomised complete block design with three replications. Data were recorded on growth, yield and drought-severity responses. The data were analysed using SAS version 9.4, and significant means were separated using the least significant difference test at α = 0.05. Significant (P < 0.05) differences were observed for all phenotypic traits assessed. Days to 50% flowering ranged from 46 (NA20) to 63 (NA53) in Trial 1 and from 45 (NA20) to 62 (NA18) in Trial 2. Grain yield ranged from 134.5 kg/ha (NA18) to 961.0 kg/ha (MA32) in Trial 1 and from 18.9 kg/ha (NA60) to 743.3 kg/ha (SY03) in Trial 2. Drought severity differed significantly (P < 0.05) at 7, 14, 21 and 28 days after imposition, and the response depended on the accession and plant growth stage. At 28 DAI, drought-severity scores ranged from 3.00 (NA53) to 6.33 (NA20) in Trial 1 and from 3.56 (MA32) to 6.50 (MA48, NA20, NA83 and NA91) in Trial 2. Eleven accessions (BS02, KK05, NA20, NA43, NA77, NA83, NA91, MA48, MA44, MA54 and NA15) had high yield potential under drought stress. Thirteen accessions (ES02, ES05, KK04, KK07, MA1, MA22, MA26, MA32, MA63, NA18, NA92, SY01 and TR01) exhibited drought tolerance with a characteristic stay-green appearance. These accessions may be used in cowpea breeding and improvement programmes to develop drought-tolerant varieties for semi-arid regions. The findings identify genetic resources that may support the development of climate-resilient cowpea cultivars.
Keywords: Cowpea, Vigna unguiculata, drought tolerance, water-deficit stress, field screening, grain yield, stay-green trait, flowering time, germplasm evaluation, semi-arid production