PCR DETECTION OF MLOS IN QUICK DECLINE-AFFECTED PEAR TREES IN ITALY

Polymerase chain reaction (PCR) amplification, using primers derived f rom the 16S rRNA gene, followed by restriction fragment length polymor phism (RFLP) analysis with Alu I restriction endonuclease was used to detect mycoplasma-like organisms (MLOs) associated with pear decline. MLOs were consistently detected in pear trees that suddenly wilted and died within a few days during summer, as well as in pears of the same orchards with symptoms similar to the slow form of pear decline. In b oth cases the same RFLP pattern was obtained. Declining pear trees wer e 5 to 8-yr-old cvs Williams, Kaiser and Max Red Bartlett grafted on t o Pyrus communis seedling rootstocks. All the orchards affected by qui ck decline had severe attacks of pear psyllid (Cacopsylla pyri) during the year this study was performed and during the previous year. The r esults showed the suitability of DNA amplification by the polymerase c hain reaction for the detection of pear decline MLOs and established t hat MLOs can be detected in infected tissues of dead trees.