An extractable agent, induced in uninfected tissues by localized virus infections, that interferes with infection by tobacco mosaic virus

Abstract

Juice extracted from uninfected apical halves of leaves of Datura stramonium previously inoculated on their basal halves with tobacco mosaic virus (TMV) or tobacco necrosis virus, a procedure known to induce resistance to TMV in the uninfected apical halves, was found consistently to interfere with infection by TMV (when mixed with it just prior to inoculation of Nicotiana glutinosa, N. tabacum var. Samsun NN, or D. stramonium) to a much greater extent than did juice from apical halves of control leaves. In some tests, a standard TMV inoculum induced only 8% as many lesions when mixed with extracts from resistant half-leaves of Datura as it did when mixed with extracts from comparable control leaves. The difference in ability of the two juices to interfere with infection by TMV was found not to be due to differences in pH nor to inactivation of the virus in vitro. The differential effect of the two types of juice was eliminated by heating at 78°C for 15 minutes but not by heating at 68° for 15 minutes, by aging at 3° for 5 days, by dialysis, or by centrifugation at 93,000 g for 1 hour. Partial purification was effected by dialysis and use of an anion-exchange cellulose; after each step in the procedure, extracts from resistant half-leaves remained more inhibitory than did those from control leaves. Evidently, infection in basal leaf halves either induced the formation in apical halves of an interfering agent (or agents) not found in healthy leaves or stimulated the production of an inhibitor (or inhibitors) normally found in Datura leaves. Extracts from resistant half-leaves of Samsun NN tobacco were sometimes, but not always, more inhibitory than extracts from control leaves.