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