Pear decline phytoplasm can affect cultivars of Japanese pear
During preliminary surveys carried out in 1991-92, in Emilia-Romagna (IT), symptoms similar to the slow form of pear decline phytoplasm (EPPO A2 quarantine pest) were observed in trees of Pyrus pyrifolia cvs Hosui and Kosui grafted on P. communis seedling rootstocks. The main symptoms were a downward curling of the distal part of the leaves with an upward rolling along the midribs of the margins. The leaves then turned red and became abnormally thick with swollen and brown major veins. The incidence of this decline was particularly high in one orchard adjacent to a pear orchard strongly affected by the slow form of pear decline. In affected trees, phytoplasms were consistently detected by using DAPI technique and RFLP analysis of PCR-amplified DNA. The authors concluded that although Japanese pears are well-known hosts of pear decline phytoplasm when used as rootstocks of French cultivars, this is the first report of pear decline in P. pyrifolia as the scion cultivar.
Poggi Pollini, C.; Giunchedi, L.; Seemüller, E.; Lorenz, K.H. (1994) Association of the decline of Nashi pears with an MLO.
Journal of Phytopathology, 142 (2), 115-121.