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African Journal of Food, Agriculture, Nutrition and Development
Rural Outreach Program
ISSN: 1684-5358 EISSN: 1684-5358
Vol. 18, No. 2, 2018, pp. 13502-13524
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Bioline Code: nd18046
Full paper language: English
Document type: Research Article
Document available free of charge
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African Journal of Food, Agriculture, Nutrition and Development, Vol. 18, No. 2, 2018, pp. 13502-13524
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PHENOTYPIC SCREENING OF COWPEA ( VIGNA UNGUICULATA (L.) WALP) GENOTYPES FOR RESISTANCE TO COWPEA VIRAL DISEASES
Tettey, CK; Asare-Bediako, E; Asare, TA & Amoatey, H
Abstract
Viruses are a major constraint to cowpea production in sub-Saharan Africa. Host plant
resistance is the most effective and reliable method of managing viral diseases. In order
to identify the source of resistance or tolerance, 38 cowpea genotypes were screened for
virus infection under field conditions during the 2016 wet and dry seasons. The
experiment was laid out in a randomized complete block design with four replications in
both seasons. Disease severity was assessed fortnightly based on disease symptom using
1-5 visual scale (1=symptomless, and 5= very severe symptom). The cowpea genotypes
exhibited varying reactions to viral infections with mean disease incidence ranging from
17.7% in the fourth week to 29.2% in the eighth week for the wet season and from 34.4%
to 53.1% for the fourth and eighth week, respectively in the dry season. Symptoms
observed were leaf mosaic (86.7%), leaf mottling (86.7%), chlorotic spots (34.2%), vein
clearing (28.9%), leaf curl (26.3%), necrotic lesions (15.8%) and stunting (10.5%).
Symptom severity in the rainy season ranged from symptomless (severity score of 1) in
IT10K-819-4 and IT07K-297-13 to moderate symptom (severity score of 2.9) in
Apagbaala. However, in the dry season, the symptom severity score ranged from 1.11
(mild symptom) in Marfo Tuya to a score of 2.4 (moderate symptom) in IT07K-298-9,
thus demonstrating a significant genotype x season interaction effect. Incidence and
severity were significantly higher in the dry season than in the rainy season. There was
a strong positive correlation between the disease incidence and disease severity as well
as AUDPC and no correlation between the cowpea incidence and the seed yield and plant
height in the wet season. There was a negative correlation between the incidence and
plant height in the dry season. Six genotypes (IT07-210-1-1, IT07K-297-13, IT08K-193-14, IT09-456, IT10K-817-3 and IT10K-819-4) exhibited mild symptoms and gave high
yields in both seasons, thus demonstrating a stable G x E interaction effect. These disease
resistant genotypes could be evaluated further before release to farmers.
Keywords
Area Under Disease Progress Curve; Host resistance; Vigna unguiculata; Viral diseases
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