ISHS Acta Horticulturae 556: V International Congress on Hazelnut
THE PROBLEM CAUSED BY PSEUDOMONAS AVELLANAE ON HAZELNUT IN ITALY |
| Author: | M. Scortichini |
| Keywords: | Corylus avellana, decline, bacterial disease, spring frost, acidic soil, “moria” |
| Abstract:
Pseudomonas avellanae is the causative agent of hazelnut decline in central Italy, the so called "moria". The bacterium is currently present in about 1,000 out of the 20,000 hectares of hazelnut orchards in the area. The main symptoms include the rapid wilting of twigs, branches and trees during spring and/or summer. Characteristically, the leaves remain attached to the twigs after their withering. Penetration mainly occurs in autumn through the leaf scars and, from there, the pathogen can move systemically within the plant, having the possibility of reaching the roots. Some factors such as acidic soils and spring frost seem to play a major role in predisposing the tree to the pathogen. Symptoms similar to those incited by P. avellanae in central Italy have also been observed in the other main areas of hazelnut production in Italy: Campania. Piemonte, Sicily and Sardinia. Genomic and phenotypic fingerprints of the populations isolated from the different geographic areas performed by means of repetitive-PCR and whole-cell protein analysis as well as artificial inoculation of hazelnut, identified two major groups of pseudomonads pathogenic to Corylus avellana in Italy: the P. avellanae group, including the strains isolated in central Italy and northern Greece, and a related but clearly different group including the different populations isolated from the other areas. P. avellanae strains are very virulent towards hazelnut germplasm, whereas the other pseudomonads proved only mildly aggressive. Finally, field trials were carried out in order to test the possibility of controlling hazelnut decline by means of acibenzolar-S-methyl, a SAR(Systemic Acquired Resistance)-inducing compound. When sprayed five times during spring and summer, at 50 g/hectare of the product containing 50% of active ingredient, this compound reduced the attack of the pathogen by 25-30% compared to the trees treated with copper oxychloride during leaf fall and budbreak. | |
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