Activation of One Plant Virus by Another

TOBACCO necrosis is a disease that can be caused by several serologically unrelated viruses1, all of which are soil-borne and cause necrotic local lesions in leaves of tobacco (Nicotiana tabacum L.) and French bean (Phaseolus vulgaris L.) plants. The virus Bawden and Pirie2,3 called the ‘Rothamsted culture’ differed in several respects from other members of the group ; the ratio of infectivity to specific antigen content varied greatly in...