First Report of Pear Decline Phytoplasmas on Nashi Pears (Pyrus pyrifolia) in France. W. Jarausch, Unitie de Recherches sur les Especes Fruitieres et la Vigne, INRA Bordeaux, BP 81, 33883 Ville-nave d’Ornon, France. F. Dosba, Unitie de Recherches sur les Especes Fruitieres et la Vigne, INRA Bordeaux, BP 81, 33883 Ville-nave d’Ornon, France. Plant Dis. 79:1250. Accepted for publication 18 October 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1250D.
Symptoms of pear decline have been observed in experimental and commercial orchards of Nashi pear (Asian pear) (Pyrus pyrifolia (N. L. Burm.) Nakai) in the southwest of France since autumn 1992. In late summer, premature leaf reddening on cv. Kosui and small chlorotic leaves on cvs. Shinseiki and Nijiseiki were observed. Leaf midribs and major veins were accentuated. Affected trees had stunted shoot growth and early leaf fall. In 1994, polymerase chain reaction (PCR) based on the specific amplification of a homologous nonconserved DNA fragment of European fruit tree phytoplasmas (1) was employed to test symptomatic Nashi trees for the presence of phytoplasmas. PCR amplification with primer pairs AP3-AP4 and AP9-AP10 was used to detect phytoplasma DNA in total DNA extracts from phloem preparations (1). No PCR product was observed on agarose gel after electrophoresis of DNA amplified with primer pair AP3-AP4 specific for Malus- and Prunus-affecting phytoplasmas (1). Amplification by primer pair AP9-AP10, which detects Pear decline phytoplasmas (1), yielded substantial PCR product of the expected size (452 bp) from 12 of 15 samples. Restriction fragment length polymorphism analyses of AP9-AP10 PCR products with restriction enzyme RsaI produced the pattern described for pear decline phytoplasmas (1). Phytoplasmas have been previously reported on Nashi trees in Italy (2). This is the first report of phytoplasmas associated with pear decline on Nashi pear in France. Among the Nashi pear cultivars tested, cv. Shinseiki appeared more susceptible as it had the most pronounced symptoms and the highest percentage of trees with symptoms.References: (I) W. Jarausch et al. Appl. Environ. Microbiol 60:2916, 1994. (2) C. Poggi Pollini et al. J. Phylopathol. 142:115, 1994.