A new apple tree's disease, probably caused by a new pathotype of Alternaria alternata, was observed for the first time in Alto Adige, in the year 2000. In the following years the disease spread southwards in Trentino and in Veneto, Piedmont, and, maybe, Emilia-Romagna. The disease usually appears in late spring on leaves as little, irregular to round, brown-reddish or black spots, sometimes with a reddish halo. Spot numbers increase during the season and they coalesce to form wide necrotic areas; affected leaves can fall prematurely. Brown-blackish spots, 0.5 to 2 mm in diameter, appear on fruits. Incidence of affected fruits varies over the years and generally increases in the pre-harvest period. Preliminary investigations showed that the Italian strains of Alternaria from both leaves and fruits are probably able to cause the disease by producing host specific toxins, but these strains do not belong to the pathotype mali of A. alternata present in other apple-growing areas of the world. A bioassay was developed for detecting the apple-pathogenic strains of Alternaria. Different inoculation methods were tested on wounded or unwounded leaves or fruits. A ring test was carried out using five fungal isolates to evaluate repeatability and reproducibility of the bioassay. Necrotic spots consistently appeared on the inoculated organs after 24-48 hours of incubation only on wounded tissues. Availability of a robust bioassay is the first step to study population dynamics of the apple-pathogenic strains, characterize strains at morphological, ecological, biochemical, and molecular levels, and investigate the host–pathogen interactions.

Preliminary investigations on Italian strains of Alternaria causing a new apple tree disease

ROTONDO, FRANCESCA;COLLINA, MARINA;BRUNELLI, AGOSTINO;
2009

Abstract

A new apple tree's disease, probably caused by a new pathotype of Alternaria alternata, was observed for the first time in Alto Adige, in the year 2000. In the following years the disease spread southwards in Trentino and in Veneto, Piedmont, and, maybe, Emilia-Romagna. The disease usually appears in late spring on leaves as little, irregular to round, brown-reddish or black spots, sometimes with a reddish halo. Spot numbers increase during the season and they coalesce to form wide necrotic areas; affected leaves can fall prematurely. Brown-blackish spots, 0.5 to 2 mm in diameter, appear on fruits. Incidence of affected fruits varies over the years and generally increases in the pre-harvest period. Preliminary investigations showed that the Italian strains of Alternaria from both leaves and fruits are probably able to cause the disease by producing host specific toxins, but these strains do not belong to the pathotype mali of A. alternata present in other apple-growing areas of the world. A bioassay was developed for detecting the apple-pathogenic strains of Alternaria. Different inoculation methods were tested on wounded or unwounded leaves or fruits. A ring test was carried out using five fungal isolates to evaluate repeatability and reproducibility of the bioassay. Necrotic spots consistently appeared on the inoculated organs after 24-48 hours of incubation only on wounded tissues. Availability of a robust bioassay is the first step to study population dynamics of the apple-pathogenic strains, characterize strains at morphological, ecological, biochemical, and molecular levels, and investigate the host–pathogen interactions.
2009
XV Congresso della Società Italiana di Patologia Vegetale
112
112
K. Marschall; E. Pattori; E. Ortalda; F. Rotondo; M. Collina; A. Brunelli; V. Rossi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/86311
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