Responses of African yam bean (&lt;i&gt;Sphenostylis stenocarpa&lt;/i&gt; [Hochst. Ex A. Rich]) accessions to viral diseases and serological identification of the associated viruses

O.M Ogunsanya,M.O Otusanya,C.G Afolabi,M.A Adebisi

doi:10.4314/njb.v37i1.9

Abstract

African yam bean (Sphenostylis stenocarpa) is an orphan crop with lofty nutraceutical benefits grown in Africa. However, pests and diseases often hinder its productivity. Twenty accessions of African yam bean (AYB) were screened for resistance to viral diseases and symptomatic leaves were indexed for the presence of viruses. The Field experiments were conducted during the 2015/2016 cropping seasons (wet and dry seasons). The twenty accessions were grown in triplicates in a randomized complete block design (RCBD) on the field under natural infection and the resistance or susceptibility responses were recorded using visual symptom expression. The characteristic symptoms that were highly prevalent were leaf mosaic and leaf distortion. In both seasons, there were significant (P< 0.05) differences in the severity of these viral symptoms. Also, based on the severity of the symptoms observed in this study, 2 accessions were classified as resistant, 16 as susceptible and 2 accessions as highly susceptible. Two viruses were identified serologically namely Cowpea Mild Mottle Virus (CPMMV) and Blackeye Cowpea Mosaic Virus (BlCMV). The sources of resistance identified in this study would be useful for breeders in developing virus resistant varieties for African yam bean improvement. Keywords: African yam bean, Virus, Symptoms, ACP-Elisa, Screening.

Highlights

African yam bean (AYB; Sphenostylis st enocarpa) is a tuberous legume which belongs to the family Fabaceae
Field screening for resistance under natural viral infection cannot rely only on visual symptoms, as it has been postulated that different viruses exhibit similar symptoms
2 viruses which corroborate the reports of Hughes et al (2003) and Ghorbani et al (2007) were identified in the AYB leaf samples collected in the second planting season namely Cowpea Mild Mottle Virus (CPMMV) and Blackeye cowpea mosaic virus (BlCMV)

Summary

Introduction

African yam bean (AYB; Sphenostylis st enocarpa) is a tuberous legume which belongs to the family Fabaceae. It is known as Diegemtenguere (Mali), Norouko and Roya (Sudan), Okpududu and Azanma (Igbo, Nigeria), Girigiri (Hausa, Nigeria) and Sese (Yoruba, Nigeria). It is mostly grown in Central (Gabon and Congo) and Western Africa (Nigeria, Cameroon, Togo, Ghana, and Ivory Coast). AYB is mostly cultivated as a mixed crop with cassava, vegetables, yam and rice The tubers of this crop possess higher protein content than sweet potato, Irish potato, yam, and cassava (Amoatey et al, 2000).

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