Phytophthora species found on diseased ornamental plants in Spain
A survey was carried out in Spain from 2001 to 2006 in order to characterize the species of Phytophthora and their host plants, and to evaluate their pathogenicity. Samples were collected from garden centres, small retailers, public and botanical gardens, and ornamental nurseries from the Comunidad Valenciana and Islas Baleares. Additional samples from Asturias, País Vasco and Cataluña were also studied. As a result, 125 isolates (31 from the mainland, 94 from Baleares) of Phytophthora species were obtained from 37 ornamental plant species, showing symptoms of root and collar rots, stem cankers, or twig and leaf blights. Most affected plants had been collected from garden centres and nurseries.
In total, 17 species or tentative species of Phytophthora could be identified during this survey. Most isolates belonged to Phytophthora species which are common in European nurseries: P. cactorum, P. cinnamomi, P. citricola, P. citrophthora, P. cryptogea, P. nicotianae, and P. syringae.
Some isolates corresponded to the following species which are less common or rare in Europe: P. drechsleri, P. hibernalis, P. palmivora, P. tentaculata, and P. tropicalis.
The following 5 species were formally unknown at the beginning of the study in January 2001 but were later described, or proposed as putative new species. P. ramorum (EPPO Alert List) was detected in Baleares (in Mallorca where it was first found in 2002 – see also EPPO RS 2002/160; and then in Ibiza) and in samples from Asturias. P. ramorum was found on Rhododendron, Viburnum, Camellia japonica and for the first time on Arbutus unedo. P. hedraiandra was detected on Viburnum tinus and Rhododendron, P. ‘niederhauserii’ on Cistus and Hedera sp., P. ‘kelmania’ on Gerbera and Coleus, and P. ‘taxon Pgclamydo’ on Rhododendron.
It is concluded that this study highlights the problems that are generated by the discovery of new or rare species of Phytophthora in ornamental nurseries. Many of them are suspected to be alien species introduced by trade of ornamental plants but little information is available on their ecology and biology. Therefore, it is difficult to predict their establishment and to evaluate their potential economic or ecological impacts on agriculture or natural ecosystems.
Moralejo E, Pérez-Sierra AM, Alvarez LA, Belbahri L, Lefort F, Descals E (2009) Multiple alien Phytophthora taxa discovered on diseased ornamental plants in Spain. Plant Pathology 58, 100-110.