The use of the polymerase chain reaction for the characterisation and diagnosis of yam potyviruses

Abstract

Yams (Dioscorea spp.) are an important tuber crop in many tropical and sub-tropical regions (Degras, 1993), especially West Africa which accounts for over 90% of world yam production (FAO, 1994). Yams, in common with other vegetatively propagated crops, are susceptible to a wide variety of different viruses (Porth & Nienhaus, 1983). Of all these viruses, the potyviruses (family Potyviridae; genus Potyvirus) are the most diverse (Porth & Nienhaus, 1983; Porth et al., 1987) and can cause significant reductions in crop yield (Thouvenel & Dumont, 1990). Of the yam-infecting potyviruses, yam mosaic virus (YMV) and yam mild mosaic virus (YMMV) are especially important, because of their high incidence and wide distribution amongst the two most widely cultivated yams; Dioscorea rotundata-cayenensis and D. alata. However, despite the importance of YMV and YMMV, very little information is available on the true level of variation found amongst these two viruses and the other potyviruses that have been reported (Porth & Nienhaus, 1983; Porth et al., 1987). This lack of knowledge on variability, coupled with the recalcitrant nature of yam tissue, has resulted in a dearth of reliable diagnostic tests. This current situation is severely hampering efforts to improve the yam crop, especially by preventing the international exchange of breeding materials. In an effort to rectify this situation, an approach using PCR-based techniques has been employed and has resulted in an increased understanding of yam potyvirus variability and the development of reliable diagnostics.KeywordsPlant Molecular Biology ReporterRecalcitrant NatureNatural Resource InstituteReliable Diagnostic TestAlternative VirusThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.