Articles
GRAY NECROSIS OF HAZELNUT FRUIT: A FUNGAL DISEASE CAUSING FRUIT DROP
Article number
845_77
Pages
501 – 506
Language
English
Abstract
In 2000, symptoms of a new emerging disease were observed in several hazelnut orchards (Corylus avellana L.) located in the Latium region.
The severity of fruit drop, and the resulting yield loss, led to investigations on the etiology and epidemiology of the disease named gray necrosis (GN) on the basis of the symptoms observed on the affected fruit.
The symptomatology is defined by the presence of brown-greyish spots at the bottom of the nuts progressing upwards to the apex, and of necrotic patches on the bracts.
Lesions progressed into the fruit involving the pericarp and embryo tissue.
On the account of four-year investigations, based on isolations from flowers, fruit and twigs, cankers developed on one-year-old vegetation, and, by artificial inoculations, it was possible to identify the fungal genera associated with the disease and give a first picture of GN which can be considered a disease complex.
The genera of fungi most commonly isolated from the edge of diseased tissues were Alternaria spp. and Fusarium spp.
Among Fusarium species, F. lateritium was always isolated from fruit affected by GN and also from typical cankers on L-shaped twigs.
Pathogenicity tests confirmed F. lateritium as the primary causal agent both for GN and for twig cankers.
Moreover, investigations on the role of small-spored catenulate Alternaria species-group involved in GN, led to the identification, on the basis of pathogenicity tests, of three distinct species-groups related to A. alternata (A. alternata, A. arborescens, A. tenuissima), which are all agents of rot of inner fruit tissues.
There is strong evidence, in accordance with the constant isolation of F. lateritium during the whole vegetative season and the reproduction of GN symptoms, that F. lateritium could be considered as the causal agent of necrosis in its pioneering role, while Alternaria taxa could be considered as secondary colonizers causing rot of inner tissues.
The severity of fruit drop, and the resulting yield loss, led to investigations on the etiology and epidemiology of the disease named gray necrosis (GN) on the basis of the symptoms observed on the affected fruit.
The symptomatology is defined by the presence of brown-greyish spots at the bottom of the nuts progressing upwards to the apex, and of necrotic patches on the bracts.
Lesions progressed into the fruit involving the pericarp and embryo tissue.
On the account of four-year investigations, based on isolations from flowers, fruit and twigs, cankers developed on one-year-old vegetation, and, by artificial inoculations, it was possible to identify the fungal genera associated with the disease and give a first picture of GN which can be considered a disease complex.
The genera of fungi most commonly isolated from the edge of diseased tissues were Alternaria spp. and Fusarium spp.
Among Fusarium species, F. lateritium was always isolated from fruit affected by GN and also from typical cankers on L-shaped twigs.
Pathogenicity tests confirmed F. lateritium as the primary causal agent both for GN and for twig cankers.
Moreover, investigations on the role of small-spored catenulate Alternaria species-group involved in GN, led to the identification, on the basis of pathogenicity tests, of three distinct species-groups related to A. alternata (A. alternata, A. arborescens, A. tenuissima), which are all agents of rot of inner fruit tissues.
There is strong evidence, in accordance with the constant isolation of F. lateritium during the whole vegetative season and the reproduction of GN symptoms, that F. lateritium could be considered as the causal agent of necrosis in its pioneering role, while Alternaria taxa could be considered as secondary colonizers causing rot of inner tissues.
Publication
Authors
A. Belisario, A. Santori
Keywords
Corylus avellana, nut disease, disease complex, Fusarium lateritium, Alternaria spp., fungal disease
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