PCR detection of pear decline in Italy
In summer 1992, quick decline of pear trees was observed in Emilia-Romagna and Veneto regions. Pear trees, apparently healthy, suddenly wilted and withered within a few days, with leaves and fruits still attached, and finally die. This form of pear decline was observed in 5-year old cv. Williams grafted onto seedling pear rootstocks (Pyrus communis) of unknown origin and on 8-year old cvs Kaiser and Max Red Bartlett grafted onto Kirchensaller seedlings. In the same orchards, the slow form of the syndrome commonly known as pear decline was also observed (pear decline MLO is an EPPO A2 quarantine pest). PCR (polymerase chain reaction), followed by RFLP was used to detect MLOs associated with pear decline. MLOs were consistently found in pear trees affected by quick and slow decline, and in both cases the same RFLP pattern was obtained, which indicates that the same pathogen is involved in these two forms. However, the authors pointed out that the possibility of the presence of more than one MLO involved in the two syndromes would need further investigation. The occurrence of different forms of pear decline in the same orchards could be due to a certain variability of rootstock susceptibility and it was noted that all orchards affected by quick decline showed high populations of pear psyllid (Cacopsylla pyri). The authors concluded that PCR was a suitable method for detecting pear decline MLOs, in wilting plants and in infected tissues of dead trees.
Sources
Giunchedi, L.; Poggi Pollini, C.; Biondi, S.; Babini, A.R. (1994) PCR detection of MLOs in quick decline-affected pear trees in Italy.
Annals of Applied Biology, 124 (2), 399-403.