Disease Note.

Detection of Pear Decline Phytoplasma in Declining Pear Trees in Poland. T. Malinowski, Research Institute of Pomology and Floriculture, 96-100 Skierniewice, Poland . J. Zandarski, Central Laboratory of Plant Quarantine, 87-100 Torun, Poland.; and B. Komorowska and B. Zawadzka, Research Institute of Pomology and Floriculture, 96-100 Skiemiewice, Poland. Plant Dis. 80:464. Accepted for publication 17 February 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0464A.

Disease symptoms including premature foliage reddening and slow decline of pear trees (cvs. Kiparyjska, Radcowka, and Williams' Bon Chretien [syn. Bartlett] grafted on Pyrus communis L.) were observed in some orchards in Poland. Quick decline of pear trees (cv. Patten on P. communis) was noted in two orchards. Samples of roots and shoots were collected and tested for the presence of pear decline phytoplasma using fluorescence microscopy (4',6-diamidino-2-phenylindole [DAPI]) and polymerase chain reaction (PCR) amplification of the fragment of 16S rRNA gene. Numerous DAPI-stained objects were observed in sieve tubes of roots of pear trees showing disease symptoms, but not in sieve tubes of healthy plants. DNA for PCR amplification was isolated as previously described (1). The primer pair fU5-rU3 that initiated amplification of the target DNA from all phytoplasmas tested and a more specific ribosomal primer pair fPD-rOl that amplified phytoplasma rDNA in all samples showing pear decline symptoms (2) were used. PCR products of about 880 bp for fU5-rU3 and about 920 bp for fPD-rOl were obtained in PCR reactions from DNA isolated from roots and leaf petioles of pear trees showing decline symptoms. No PCR products were observed for healthy plants. PCR products obtained from diseased plants were digested with AluI restriction enzyme and showed the restriction fragment length polymorphism patterns expected for pear decline, confirming the specificity of the reaction. This is the first report in Poland regarding detection of a pear decline phytoplasma in declining Pyrus spp.