First Report of Phytophthora spp. as Pathogens of Pandorea jasminoides in Italy.

In the summer of 2005, approximately 5% of a nursery stock of 12-month-old potted plants of bower vine (Pandorea jasminoides (Lindl.) K. Schum.) in Sicily (Italy) showed wilt, leaf chlorosis, defoliation, root rot, and collapse of the entire plant. Three Phytophthora spp. (20, 50, and 30% of the isolations of the first, second, and third species, respectively) were isolated from rotted roots on BNPRAH selective medium (2). Single-hypha isolates of the first species formed petaloid colonies on potato dextrose agar (PDA) and had an optimum growth temperature of 25°C (9.3 mm/day); on V8 juice agar, they produced uni- and bipapillate, ovoid to limoniform sporangia with mean dimensions of 45 × 30 µm and a mean length/width (l/w) ratio of 1.4:1. They did not produce gametangia when paired with A1 and A2 isolates of Phytophthora nicotianae. The second species formed arachnoides colonies on PDA, had an optimum growth temperature of 30°C (6.9 mm/day) and produced sporangia that were uni- and bipapillate, ellipsoid, ovoid, or pyriform to spherical (dimensions 44 × 34 µm; l/w ratio 1.3:1). All isolates were A2 mating type and produced amphyginous antheridia and spherical oogonia with smooth walls. The third species formed rosaceous colonies on PDA, had an optimum growth temperature of 28 to 30°C (11.9 mm/day), and produced uni- and bipapillate, ellipsoid or limoniform, caducous sporangia (dimensions 52 × 26 µm; l/w ratio 2.1:1) with a tapered base and a long pedicel (as much as 150 µm). All isolates were A1 type and produced amphigynous antheridia and spherical oogonia with smooth walls. The three species were identified as P. citrophthora, P. nicotianae, and P. tropicalis, respectively. The electrophoretic analysis of the mycelial proteins and four isozymes (1) confirmed the identification. Blast analysis of the sequence of the internal transcribed spacer region of the rDNA of a P. tropicalis isolate from bower vine (GenBank Accession No. EU076731) showed 99% similarity with the sequence of a P. tropicalis isolate from Cuphea ignea (GenBank Accession No. DQ118649). The pathogenicity of three isolates from bower vine, IMI 395552 (P. citrophthora), IMI 395553 (P. nicotianae), and IMI 395346 (P. tropicalis), was tested on 3-month-old potted bower vine plants (10 plants for each isolate) by applying 10 ml of a suspension (2 × 104 zoospores/ml) to the root crown. The plants were maintained at 24°C and 95 to 100% relative humidity. All inoculated plants wilted after 4 weeks. Noninoculated control plants remained healthy. The three Phytophthora spp. were reisolated from symptomatic plants. To our knowledge, this is the first report of Phytophthora root rot of bower vine in Italy. References: (1) S. O. Cacciola et al. Plant Dis. 90:680, 2006. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996.

First Report of Bud Rot of Canary Island Date Palm Caused by Phytophthora palmivora in Italy.

Canary Island date palm (Phoenix canariensis hort. ex Chabaud) is planted as an ornamental in Mediterranean climatic regions of the world. From 2004 to 2006, withering of the spear leaf was observed on screenhouse-grown potted plants of this palm in Sicily (Italy). The first symptom was a dark brown rot that extended from the petiole base of the spear to the adjacent youngest leaves and killed the bud. Dissection of plants revealed a foul-smelling internal rot. After the bud died, external older leaves remained green for months. As much as 10% of plants in a single nursery were affected. A Phytophthora species was consistently isolated from symptomatic plants on BNPRAH selective medium (4). Single zoospore isolates were obtained from the colonies. The species isolated was identified as Phytophthora palmivora (E. J. Butler) E. J. Butler on the basis of morphological and cultural characteristics (3). On V8 juice agar, the isolates produced elliptical to ovoid, papillate sporangia (33 to 77 × 22 to 38 µm) with a mean length/breadth ratio of 1.8. Sporangia were caducous with a short pedicel (mean pedicel length = 5 µm) and had a conspicuous basal plug. All isolates were heterothallic and produced amphigynous antheridia, oogonia, and oospores when paired with reference isolates of P. nicotianae and P. palmivora of the A2 mating type. The oogonium wall was smooth. Identification was confirmed by electrophoresis of mycelial proteins in polyacrylamide slab gels (1). The electrophoretic patterns of total mycelial proteins and four isozymes (alkaline phosphatase, esterase, glucose-6-phosphate dehydrogenase, and malate dehydrogenase of the isolates) from Phoenix canariensis were identical to those of P. palmivora reference isolates, including four Italian ones, two from pittosporum and olive, respectively, and two (IMI 390579 and 390580) from Grevillea spp. Phoenix canariensis isolates were clearly distinct from those of other heterothallic papillate species including P. capsici, P. citrophthora, P. katsurae, P. nicotianae, and P. tropicalis. Pathogenicity of one isolate from Phoenix canariensis (IMI 395345) was tested on 10 2-year-old potted Canary Island date palm plants. An aqueous 105 zoospores per ml suspension (200 µl) was pipetted onto unwounded petiole bases of the three youngest central leaves of each plant. Sterile water was pipetted onto 10 control plants. All plants were incubated in 100% humidity at 24°C for 48 h and maintained in a greenhouse at 20 to 28°C. Within 3 weeks after inoculation, inoculated plants developed symptoms identical to those observed on plants with natural infections. Control plants remained healthy. P. palmivora was reisolated from symptomatic plants. Phytophthora bud rot is a common palm disease worldwide and Phoenix canariensis is reported as a host (2). To our knowledge, this is the first report of Phytophthora bud rot on Phoenix canariensis in Italy. References: (1) S. O. Cacciola et al. EPPO Bull. 20:47, 1990. (2) M. L. Elliot et al., eds. Compendium of Ornamental Palm Diseases and Disorders. The American Phytopathological Society, St. Paul, MN, 2004. (3) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (4) H. Masago et al. Phytopathology, 67:425, 1977.