New Disease Reports (2009) 20, 23.

Phytophthora alni on Alnus glutinosa reported for the first time in Spain

A. Solla 1, A. Pérez-Sierra 2, T. Corcobado 1, M.M. Haque 3, J.J. Diez 3 and T. Jung 4,5*

*competence@tree-diseases.com

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Accepted: 01 Dec 2009

Since the mid 2000s extensive mortality of common alder (Alnus glutinosa) has been observed along many rivers of northern Spain (Tuset et al., 2006). Symptoms include sparse yellowish and small-sized foliage, dieback of branches, increased fruit production and dark-stained necrosis of the bark at the collar and lower stem. These resemble symptoms of the root and collar rot epidemic of alders which is caused bythe different subspecies of the host-specific pathogen Phytophthora alni and has led to high mortality of riparian alders across 14 countries in Western, Central and Northern Europe (Gibbs et al., 2003; Jung & Blaschke 2004).

In September 2009, samples from five symptom-bearing A. glutinosa trees were collected along the river Miño ( Lugo, Galicia , 42º59’N 7º32’W, 367 m above sea level). Bark samples, including the cambium, were taken from the upper 20 cm of the orange-brown active lesions, placed in distilled water and transported to the laboratory in cool jars. Over 2-3 days the water was replaced four times per day in order to remove excess polyphenols. Small pieces (c. 4 x 4 x 2 mm) were cut from the lesions, blotted dry and plated onto V8-PARPH agar (Jung & Blaschke, 2004). After five days incubation at 20°C, tentative Phytophthora isolates were obtained from four trees. The isolates were homothallic with amphigynous antheridia, predominantly two-celled, and produced ornamented, occasionally comma-shaped oogonia ranging from 33 to 50 μm in diameter. In soil-extract they produced nonpapillate, ellipsoid to ovoid sporangia (60 x 49 μm). On V8 agar, colonies had a slightly woolly morphology and showed radial growth rates of 3.6-7.5, 2.2-5.4 and 0.0 mm/day at 20, 25 and 30°C, respectively. These features resemble those of P. alni ssp.alni (Brasier et al., 2004). DNA of the ITS region was amplified as described previously (Cooke et al., 2000). The sequences of all isolates were identical (GU175431) and a blast search at GenBank showed 99% identity with P. alni ssp. alni (AF139366.1). This is the first report of P. alni in the Iberian Peninsula . Additional surveys will be carried out, which will allow the administration to adopt proper management strategies.  

Acknowledgements

To O. Locos and to P. Abad-Campos. Supported by Consejerías ECI and IEMA (Junta de Extremadura, III-PRI 08-A78), University of Valladolid (061/060831), and Ministerio Educación y Ciencia (AGL2007-64690/AGR).


References

  1. Brasier CM, Kirk SA, Delcan J, Cooke DEL, Jung T, Man in't Veld WA, 2004. Phytophthora alni sp. nov. and its variants: designation of emerging heteroploid hybrid pathogens spreading on Alnus trees. Mycological Research 108, 1172-1184.
  2. Cooke DEL , Drenth A, Duncan JM, Wagels G, Brasier CM, 2000.A molecular phylogeny of Phytophthora and related oomycetes.Fungal Genetics and Biology 30, 17–32.
  3. Gibbs JN, Van Dijk C, Webber JF, eds, 2003. Phytophthora disease of alder in Europe . Forestry Commission Bulletin 126. Edinburgh, UK : Forestry Commission.
  4. Jung T, Blaschke M, 2004. Phytophthora root and collar rot of alders in Bavaria : distribution, modes of spread and possible management strategies. Plant Pathology 53, 197-208.
  5. Tuset JJ, González V, Hinarejos C, Mira JL, Sánchez G, 2006. Prospección para determinar la posible presencia de Phytophthora spp. en las alisedas del norte de España. In: Proceedings of the XXIII Annual Meeting of the Forest Health Working Group, Madrid, Spain, 2006, Comunidad Autónoma de Madrid: 527-537.

This report was formally published in Plant Pathology

©2009 The Authors