Anatomic effects of the viruses of Pierce's disease and phony peach

Abstract

Abstract does not appear. First page follows. Introduction Previous investigations have shown that in its method of transmission Pierce’s disease virus is closely associated with the xylem of the hosts (Houston et al., 1947).3 Furthermore, the external symptoms of the diseases caused by this virus—Pierce’s disease of the grape and dwarf disease of alfalfa—suggest a disturbance in the water-conducting system (Hewitt et al., 1942b); (Weimer, 1931). At present no other virus is known to be so definitely associated with the xylem as that of Pierce’s disease. A study of the pathological anatomy of the hosts of this virus is therefore of particular interest in the problem of tissue relations of viruses. The investigation reported in this study was undertaken to determine whether the anatomic symptoms occur in the xylem and to what extent, if at all, they are restricted to this tissue. An attempt was also made to determine the nature and location of the first signs of histopathological disturbances. This was done through developmental studies on infected grape seedlings and cuttings of alfalfa. Certain viruses cause degenerative changes in the xylem, without necessarily being limited to this tissue. Among these, the psorosis virus is particularly well known. The anatomy of the affected wood of citrus has been described (Fawcett and Bitancourt, 1943); (Webber and Fawcett, 1935). Phony peach virus also appears to cause disturbances in the xylem (Hutchins, 1933), but the information concerning its anatomic effects on this tissue is not available. The pathological anatomy of phony peach roots has been briefly considered in the present study in order to obtain additional information on the effect of viruses on the xylem.