Occurrence of Xanthomonas arboricola pv. corylina on hazelnut orchards in Sardinia and Sicily

In the course of field surveys carried out in hazelnut
(Corylus avellana) orchards of Sardinia [Barbagia di Belvì
(Nuoro)] and Sicily [Nebrodi (Messina) and Etna (Catania)]
symptoms resembling those incited by Xanthomonas
arboricola pv. corylina Vauterin et al. were observed.
Brownish, elliptical, water-soaked necrotic spots were
present on fruit husks and, sometimes, twigs showed partial
die-back. Tissues from lesion margins were ground in
a mortar containing physiological sterile saline. Aliquots
(0.1 ml) of serial ten-fold dilutions of the homogenate
were plated on Yeast extract-dextrose-calcium carbonate
agar and incubated at 25-27°C for three days. The resulting
circular, mucoid, yellowish colonies were subjected to
biochemical and pathogenicity tests, as well as repetitivesequence
PCR and fluorescent AFLP analysis in comparison
with the reference strain of X.a. pv. corylina NCPPB
2896 (National Collection of Plant Pathogenic Bacteria,
York, UK). All isolates from Sardinia and Sicily were
starch and esculin-positive, had an oxidative glucose metabolism,
and grew at 35°C. Genetic fingerprinting
showed a strong similarity of the isolates with NCPPB
2896. Pathogenicity tests, made according to Scortichini
et al. (2002), showed that all tested isolates induced wilting
of inoculated hazelnut twigs. Re-isolations yielded the
same colony type as in the primary isolations. We conclude
that the agent of the disease observed in hazelnut
orchards in Sardinia and Sicily is X. a. pv. corylina. This is
the first report of this pathogen in both islands.

Scortichini M., Rossi M.P., Marchesi U., 2002. Genetic, phenotypic
and pathogenic diversity of Xanthomonas arboricola
pv. corylina strains, question the representative nature of
the type strains. Plant Pathology 51: 374-381.