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Phytophthora × pelgrandis Causes Root and Collar Rot of Lavandula stoechas in Italy

August 2013 , Volume 97 , Number  8
Pages  1,091 - 1,096

Roberto Faedda, Santa Olga Cacciola, and Antonella Pane, Department of Agri-food and Environmental Systems Management, Plant Pathology Section, University of Catania, Catania, Italy; András Szigethy and József Bakonyi, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary; Willem A. Man in't Veld, Plant Protection Service, Ministry of Economic Affairs, Agriculture and Innovation, Wageningen, the Netherlands; Patrizia Martini, Istituto Regionale per la Floricoltura, Sanremo, Italy; and Leonardo Schena and Gaetano Magnano di San Lio, Department of Agraria, University Mediterranea of Reggio Calabria, Italy

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Accepted for publication 4 February 2013.

In 2007, Phytophthora isolates with atypical morphological and biological characteristics were found associated with root and collar rot of potted plants of Stoechas lavender (Lavandula stoechas) in an ornamental nursery in Italy. A polyphasic approach, including morphological and cultural observations, sequencing the ITS-rDNA region, the Pheca and the mitochondrial coxI genes, multiplex PCRs with primers specific for P. nicotianae or P. cactorum, as well as random amplified polymorphic DNA–polymerase chain reaction, was used to characterize these isolates. On the basis of morpho-cultural and molecular analyses, the isolates from Stoechas lavender were identified as Phytophthora × pelgrandis, a natural hybrid of P. nicotianae × P. cactorum previously reported in other European countries, the Americas, and Taiwan, as a pathogen of ornamentals and loquat plants. In pathogenicity tests using potted plants of Stoechas lavender, the P. × pelgrandis isolates, similarly to the parental species P. nicotianae, induced the symptoms observed on plants with natural infections and were reisolated only from artificially inoculated plants. Dispersal of P. × pelgrandis on this host could exacerbate the damage caused by Phytophthora root and collar rot, of which the main causal agent presently is P. nicotianae on lavender in Europe. Application of hygienic measures is important to reduce the proliferation and spread of the Phytophthora hybrids.

© 2013 The American Phytopathological Society