Abstract
During the course of the epidemiological survey of virus diseases of tobacco plants, a new strain of potato virus Y (PVY) was isolated from Burley tobaccos.
PVY was fairly prevalent in Burley tobacco and was isolated from 25 out of 40 collected samples. Most of the isolates were considered as ordinary strain. Two isolates (A-1 and A-2) caused yellow spots or yellow ring spots and sometimes necrotic brown or white small spots on systemically infected leaves of White Burley and some of domestic tobaccos. On Bright Yellow tobacco it caused veinbanding symptoms same as those of ordinary strain.
Pepper (Capsicum annuum, cultivar Takanotsume) showed necrotic lesions on inoculated leaves, and also on systemically infected leaves by the infection of all these PVY isolates. It may be useful for differential and quantitative assay host of PVY.
Thermal inactivation point of crude sap of tobacco leaves infected with A-1 isolate was 60-65°C (10min.), dilution end point 1:104 and longevily in vitro 5-6 days at 25°C. Cross protection between the ordinary strain as the first virus and A-1 isolate as the second virus was complete. No protection was observed against tobacco etch virus (Riverside strain) used as the second virus. Antiserum prepared by the injection of purified A-1 isolate to rabbits with adjuvant has positive reactions to the ordinary strain but the titer was lower than that of homogeneous antiserum-antigen reactions. Electron microscopy of the new strain showed fibrous particles with about 700mμ in length.
A-1 isolate resembles tobacco yellow spotted streak strain (Tomaru and Hidaka, 1954) which was isolated from Bright Yellow tobacco in Japan, but different from each other in symptoms on tobacco cultivars and in properties of virus sap. On the symptoms in White Burley tobacco, it resembles one of the isolates in Brazil (Silberschmidt et al, 1954), but the identity is not clear. A-1 isolate may belong to the group of necrotic strain of PVY.
