Potato virus A lesions onPhysalis species

PVA produces distinct local lesions on open leaves ofPhysalis floridana, as does PVY. But, whereas PVA induced such lesions on detached leaves, PVY did not. PVX induced similar lesions, thus the test for PVA will be most useful in work with isolated cultures of PVA or with virus tested seed lines or in screening for resistance, where PVX is absent.P. floridana plants and leaves were best held at 15 to 18 C with low light intensity (4–5 K lux). From 4–6 week old potato plants, PVA was best obtained from lower leaves, ground in 0.05 M glycine — 0.03 M phosphate buffer, pH 9.2. One leaf disc infected with PVA could be detected in a composite sample with 9 discs from healthy leaves.P. angulata andP. pubescens may also be used for diagnosis of PVA. PVY becomes systemic in these species without inducing local lesions.