Studies on the dwarf disease of mulberry tree

Abstract

The dwarf disease of mulberry tree had been considered to be a physiological trouble induced by severe pruning and plucking the leaves in the summer until 1931, when Akiya demonstrated that the disease was graft-transmissible and Ikata and Matsumoto succeeded in transmitting it by means of a leafhopper, Hishimonus discigutus (Walker), suggesting that this disease may be caused by a virus.The present author tried a series of grafting experiments to transmit this disease during the period from 1957 to 1960. The disease could not be transmitted-no disease symptom was produced-by stem-grafting when the diseased scions collected in winter were grafted on healthy stocks in April. Moreover it was found that the diseased scions became recovered producing new healthy shoots. But by crown-grafting in which healthy scions were grafted on the diseased stocks, the disease was readily transmitted to the healthy scions.Most, plant virus diseases are transmitted to the healthy host plants by budding or stem-grafting and it is rather peculiar that the mulberry dwarf disease is not transmitted by stem-grafting but by crown-grafting.