|Riassunto in Inglese:|
n this chapter an overview on the olive graft-transmissible pathogens and on the latest phytosanitary directives embodied by the EU and by the Italian Ministry of Agriculture is given.
As remarked, olive has always been considered a very resistant species to diseases caused by different pathogens; however, several pathogens, mainly systemic, can affect the trees and, in some case, invalidate the production. Recent advances in plant pathology and molecular biology, significantly contributed to the discover of new olive pathogens, to characterize their genome, biology and epidemiology.
Italy has been amongst the first Countries to adopt an effective certification system for the production of plant propagation material with high quality standards. After 10 years from its promulgation the Italian Regulation has been revised with the support of a technical committee, in order to improve the program and meet the quality standards amended in the late ‘90 by the EU, which are mandatory for all member States. In 2006 a revised national Regulation was issued (DM 20/11/2006), updating the list of pathogens that need to be checked and implementing the protocols for their identification. In the last 5 years several valuable virus-free and true-to-type primary sources, belonging to the most widespread or local Italian varieties, have been registered, propagated through the certification system, and made available to the growers. Although, the EU directives and the Italian regulations concerning the production of olive propagation material have been critically revised and implemented, it is necessary to continuously update the list of the pathogens and the diagnostic protocols, including the latest tools for genetic and phytosanitary assessment. It should be considered for example that some specific olive viruses such as OLV-1, OLV-2 and OLRSV are rare, infections are symptomless on olive plants, and there are no evidences about their threat to other crops. OLYaV is currently included in the list of the harmful pathogen for the Italian phytosanitary regulation, but even if OLYaV-infected trees are widespread, there are very few plants showing symptoms of yellowing, and more importantly the association of this virus with the OLY disease has not been clearly demonstrated. Regarding CMV and TNV, although these viruses are polyphagous and very damaging to other crops, they in olive are rare (CMV) or present only in a restricted geographical area (TNV- Portugal). On the basis of these data, the list of the viruses to be included in the phytosanitary certification program could be restricted to the following: SLRSV, CLRV (both are associated to manifest diseases either in olive plants or in other crops), ArMV (one of the harmful pathogens for Fragaria, Rubus and other crops) and perhaps TNV. Whereas, it is important to ensure that the certified olive material is free from phytoplasmas, V. dahliae and P. savastanoi pv. savastanoi.
Long distance movement of plant propagation material and the expansion of olive crops in new areas impose the use of common and harmonized certification procedures which are crucial to restrict the spread of harmful pathogens and pests.