Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

First report of Phytophthora gonapodyides involved in the decline of Quercus ilex in xeric conditions in Spain.

Abstract

In October 2009, a Phytophthora species was isolated from roots and from rhizosphere soil of a single tree located in Malpartida de Plasencia, Spain, using young Quercus robur and Q. ilex leaves as baits and V8-PARPH agar as a selective medium. The heterothallic isolates formed irregularly branched hyphae. Non-papillate elongated-ovoid to obpyriform sporangia with exit pores were produced. The colony pattern on V8 agar was stellate, and the average radial growth rates at 20, 25 and 30°C were 2.5-2.7, 2.5-2.7 and 2.2-2.3 mm/day, respectively. All these features are typical of P. gonapodyides. The identity was confirmed by sequencing the internal transcribed spacer region of the rDNA with the primers ITS4/ITS6 (GenBank Accession No. GU724194). Pathogenicity tests on one-year-old Q. ilex seedlings were performed. At 3 months after inoculation, mortality of infected plants was 53%, and mean survival time of infected plants was 71±15 days. For comparison, additional plants were inoculated in the same way with P. cinnamomi. After 3 months, mortality of Q. ilex seedlings was 94% and mean survival time of 28±7 days. The pathogens were consistently re-isolated from the roots of the dead plants. Control plants did not show any symptoms of disease. This is thought to be the first report of P. gonapodyides in Spain.