Grasspea Severe Stunt Virus Disease in Ethiopia

Abstract

Symptoms suggestive of virus infection, notably severe stunting and yellowing, were observed in grasspea (Lathyrus sativus L) crop at different locations in the country. As high as 25 % incidence was observed in some farmers’ fields although in most cases, typical symptoms were observed at a lower incidence. The causal agent was not transmitted by mechanical inoculation but was readily transmitted by aphids Acyrthosiphon pisum and Aphis craccivora from infected grasspea to healthy grasspea, faba bean, lentil, field pea and cowpea under greenhouse conditions. When field collected samples with severe stunting and yellowing symptoms were tested serologically against antisera of twelve viruses known to infect legumes by tissue blot immunoassay, most were positive for faba bean necrotic yellows nanovirus (FBNYV). Electron microscopic studies on selected serologically positive samples confirmed the
presence isometric particles of about 20 nm diameter. No other virus was detected in the samples tested. This is the first report of a virus naturally infecting cultivated grasspea in Ethiopia and elsewhere. Due to heavy colonization of most grasspea fields with the pea aphid (Acyrthosiphon pisum), it is suspected that this aphid is most likely the natural vector of FBNYV in Ethiopia.