Reversible changes in strains of tobacco mosaic virus from leguminous plants

SUMMARY: Strains of tobacco mosaic virus (TMV) obtained from systemically-infected leguminous plants in Nigeria and India changed their properties greatly when propagated in different hosts. From systemically-infected tobacco, they closely resemble type TMV and share many antigens with it, but from systemically-infected French bean, they differ from it by at least as much as any previously described strains. The different forms of the viruses share few antigens, have different amino acid constitutions, electrophoretic behaviour and resistance to inactivation by ultra-violet radiation, and they produce different kinds of local lesion in Nicotiana gluti-nosa. Isolates derived from single local lesions behave like the original bulk cultures, and as the changes are also reversible they seem unlikely to occur simply because different hosts select different strains from existing mixtures. The electrophoretic patterns, particularly of preparations from beans, show that infected plants contain more than one anomalous product; both forms of the viruses may be produced in all hosts, but there is no evidence that sap from systemically-infected beans contains the tobacco forms in amounts needed to cause infection. The change after transfe