Distribution, incidence and severity of viral diseases of yam (Dioscorea spp.) in Cte dIvoire

Abstract

A survey was conducted in major yam cultivation zones in Côte d'Ivoire in 2009 to determine the incidence, severity of viral diseases, and viruses associated with the infected plants. Incidence and severity of the viral diseases were estimated based on symptoms. Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR)-based techniques were used for the detection of Yam mosaic virus (YMV), Cucumber mosaic virus (CMV), Dioscorea mottle virus (DMoV) and yam badnaviruses in the sampled yam leaves. Disease incidence varied from 0 to 90% and symptom severity from 1 to 5. There were significant difference in incidence and severity between different agro-ecological zones (P<0.001). About 36% of the samples tested positive to YMV, ca. 1.5% tested positive to CMV, ca. 39.1% samples tested positive to yam infecting badnaviruses, and none of the samples tested positive to DMoV. This study demonstrated high incidence of virus diseases in all the yam production regions and warrants implementation of virus disease control measures.

Molecular Viral Diagnosis and Sanitation of Yam Genetic Resources: Implications for Safe Yam Germplasm Exchange

“…Surprisingly, none of the accessions were infected by CMV, although this virus has one of the broadest host spectrum ranges among plant viruses [ 55 ]. CMV was detected in yam in sub-Saharan Africa with a low prevalence [ 56 , 57 ], and viral particles of CMV were reported in yam in Guadeloupe [ 16 ]. However, the virus could not be detected by molecular tests despite numerous attempts using several sets of primers, suggesting that isometric particles of another yam-infecting virus such as DMaV were confused with CMV virions or that available molecular detection tools are not able to detect CMV isolates that may be present in Guadeloupe.…”

Detection and diversity of viruses infecting African yam (Dioscorea rotundata) in a collection and F1 progenies in Côte d'Ivoire shed light to plant‐to‐plant viral transmission

“…Yams are primarily propagated vegetatively, leading to an accumulation of viruses resulting in multiple infections (Eni et al, 2008 ). Although the impact of viral diseases on yam production is poorly documented, decreases in yield and reduction of the quality of harvested tubers due to viral infections have been reported by Toualy et al ( 2014 ), sometimes threatening entire productions. While infected tubers ensure the spread of viruses, several yam viruses are known to be transmitted by insects.…”

“…In West Africa, five distinct viruses are usually detected in yam, including YMV, yam mild mosaic virus (YMMV; genus Potyvirus ), CMV, DBV, and Dioscorea latent virus (DLV; genus Potexvirus ) (Eni et al, 2008 ; Toualy et al, 2014 ). In Côte d'Ivoire, yam growers report increasing yield losses and observe virus‐like symptoms such as chlorosis, mosaic, deformation on leaves, and dwarfism (Séka et al, 2009 ; Toualy et al, 2014 ). As a consequence, farmers increase cultivated areas in order to compensate for yield losses and maintain production levels, resulting in conflicts over land use and to negative impacts on the environment.…”

“…by Toualy et al (2014), sometimes threatening entire productions. While infected tubers ensure the spread of viruses, several yam viruses are known to be transmitted by insects.…”

A Sequence-Independent Strategy for Amplification and Characterisation of Episomal Badnavirus Sequences Reveals Three Previously Uncharacterised Yam Badnaviruses

“…Badnaviruses contain three open reading frames (ORFs) on the positive DNA strand of their genome with each strand having a single discontinuity [ 17 , 18 , 19 , 20 ]. Since the first report of a DBV in D. alata from the Caribbean in the 1970s [ 21 , 22 ], several hundred partial reverse transcriptase (RT)-ribonuclease H (RNaseH) sequences have been characterised [ 2 , 8 , 9 , 11 , 12 , 23 , 24 ]. Analyses of these sequences led to the proposition of 12 badnavirus species in Dioscorea spp.…”