THE VIRUSES CAUSING TOP NECROSIS (ACRONECROSIS) OF THE POTATO

It is shown that top necrosis can be produced in different potato varieties by a number of viruses. The reactions of these viruses on a large number of commercial varieties are given, together with certain of their properties and methods by which they can be transmitted. By grafting and needle inoculating infected potatoes to the four varieties Epicure, Arran Victory, President and Up-to-Date, and noting the type of necrotic disease produced on these differential hosts, it has been found possible to distinguish with a fair degree of accuracy between six viruses. The necrotic reactions of these varieties are given below.
The writer has great pleasure in expressing his gratitude to Dr D. R,. Salaman for permission to make use of the virus material, and for many valuable suggestions.