A New Phytophthora Root Disease of Alder in Italy

Abstract

A Phytophthora was found associated with wilt and mortality of Italian alder (Alnus cordata) seedlings in a nursery in northern Tuscany, Central Italy. This disease is one of the major constraints to alder survival in northern Europe (3). Symptoms included sparse yellowish brown foliage with abnormally small leaves, dark stained necrosis of the bark at the collar level, and reduction of the root system due to the death of the tap root and lateral roots. These symptoms resemble those on chestnut, walnut, and oak plantlets colonized by P. cambivora. The diseased seedlings were 1 to 2 years old and were grown on both beds and soil. Tissue isolation from infected parts of the plants yielded a P. cambivora-like species in culture. Pure cultures were appressed and felty in appearance with sparse or no aerial mycelium when grown on V8 agar, carrot agar, or potato dextrose agar. Sporangia were ovoid, non-papillate, and averaged 51.8 μm in length and 36.6 μm in width (range: 45 to 60 μm and 30 to 40 μm). The isolates were homothallic with smooth-walled oogonia with a diameter ranging from 20 to 45 μm and with two-celled, amphigynous antheridia. Colonies showed rapid development at 25°C (mean radial growth = 6 mm/day), but at 30°C growth was strongly inhibited, unlike P. cambivora isolates previously collected in the same area, which were more thermophilic. The morpho-physiological features of the alder isolates resembled those of the Swedish variant of the alder Phytophthora (2). Identification was confirmed by C.M. Brasier (Forestry Authority Research Station, UK). Two-year-old alder seedlings (1.3 cm diameter, height 70 cm) grown in pots were wound-inoculated in the trunk. Six weeks after inoculation, symptoms were produced identical to those described above, as well as necrosis of the bark tissue varying in length from 0.5 to 3 cm. Isolations from diseased bark tissue yielded fungal colonies resembling those described above. The pathogen, described for the first time in England in 1995 (1), is now present throughout northern Europe. This is the first report for the Mediterranean region, which suggests that the fungus will cause disease in the drier and warmer climates of southern Europe. References: (1) C. M. Brasier et al. Plant Pathol. 44:999, 1995. (2) C. M. Brasier et al. Proc. Natl. Acad. Sci. USA 96:5878, 1999. (3) J. N. Gibbs et al. Eur. J. For. Pathol. 29:39, 1999.

Susceptibility of common alder (Alnus glutinosa) seeds and seedlings to Phytophthora alni and other Phytophthora species

“…alni has appeared as a highly aggressive pathogen on seeds and seedlings of A. glutinosa. The high aggressiveness of P. alni has been already stated by other authors in several European countries (Brasier et al, 1995;Gibbs, 1995;Szabó et al, 2000;Santini et al, 2001;Streito et al, 2002;Nagy et al, 2003;Jung and Blaschke, 2004;Cerný and Strnadová, 2010;Solla et al, 2010;Varela et al, 2010). Pathogenic ability of P. alni on seeds of A. glutinosa has been revealed from a similar laboratory test made by Schumacher et al (2006), where seeds were inoculated with a zoospore suspension.…”

“…In Italy, P. alni was found infecting A. cordata both in young plantations and nurseries (Santini et al, 2003). Several other authors have also reported the association of P. alni with alder seedlings in plantations and nurseries (Santini et al, 2001;Gibbs et al, 2003;Schumacher et al, 2006). So, we assume that P. alni ssp.…”

“…The association of P. alni in the decline and mortality process of alders has been the center point of several studies in different parts of the world (Gibbs, 1995;Gibbs et al, 1999;Santini et al, 2001;Brasier and Kirk, 2001;Brasier, 2003;Gibbs et al, 2003;Santini et al, 2003;Jung and Blaschke, 2004;Ioos et al, 2005;Cerný and Strnadová, 2010;Solla et al, 2010;Varela et al, 2010). Phytophthora decline of the riparian alder population has recently become an important problem in Spain because of the rapid spreading of the causal pathogen.…”

Early-screening for resistance toPhytophthorasp.p. in wild cherry clones (Prunus aviumL.)

“…P. megasperma ha mostrato un diverso grado di aggressività nei confronti dei cloni testati determinando gravi sintomi su ACW10, VM02 e AP06 e sintomi minori sul clone VTS02, sia nella prima che nella seconda prova. La P. alni è stata recentemente segnalata in Italia su ontano sia in vivaio (Santini et al 2001) che in impianti da legno (Anselmi et al 2001). Dai risultati qui ottenuti non sembra che sussista il rischio che questo patogeno possa passare da ontano a ciliegio.…”

“…Sebbene in Italia gli studi sul patosistema ciliegioPhytophthora siano ancora pochi, un'importante segnalazione di questo patogeno su ciliegio si ha nella provincia di Arezzo, dove P. megasperma è stata iso-lata da piante deperienti in una collezione clonale dell'Istituto Sperimentale per la Selvicoltura (Motta et al 1997). Recentemente in Italia (Santini et al 2001, Anselmi et al 2001) è stata segnalata la presenza di P. alni su ontano. La comune consociazione di questa specie al ciliegio negli impianti per la produzione legnosa rende necessario indagare la patogenicità di questo nuovo taxon su ciliegio.…”