POTATO VIRUS DISEASES

THE degeneration of the potato seems to have been unknown in Europe before about 1770, but after that it rapidly assumed such proportions that by 1780 farmers in some districts had to abandon potato growing, and prizes were offered to those who could find the cause and devise a cure for this serious affliction of so important a crop. For 150 years there was continual speculation and controversy about the cause of this degeneration. Some shrewd observers drew deductions that recent work has fully confirmed, but in the absence of any direct experimental evidence the most widely held view was that potatoes degenerate because they are weakened by continual propagation by 'unnatural' asexual methods. Only within the last twenty years has it become clear that degeneration is a result of plants becoming infected with one or more viruses, which are handed on to the progeny through tubers, but rarely, if ever, through the true seeds. If one can judge from the size of the audience at a discussion on this subject, arranged jointly by the Association of Applied Biologists and the British Mycological Society*, on October 9, this advance in our knowledge has certainly not lessened interest in the problem.