**1. Introduction**

106 Olive Germplasm – The Olive Cultivation, Table Olive and Olive Oil Industry in Italy

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Olive plants are among the most ancient cultivated fruit trees. Over the centuries, propagation occurred mainly vegetatively. The longevity of trees and the latency of most of the virus infections allowed the dissemination through the propagative material of hidden viruses, which were not detected until recently, when the advent of novel diagnostic tools surprisingly revealed that virus infections are in fact widespread.

In the past, the selection of high value olive germplasm has been mainly based on the agronomic and pomological traits of the plants and on the quality and yield of the olivederived product (oil). Specifically, investigation on the sanitary status of the selected ecotypes were done mainly by visually inspections. This fact leaded to the propagation and spread of systemic pathogens harbored either in a latent form or in the form of specific symptoms that initially have been confused with the phenotypic expression of the plant (as in the case of symptoms caused by infection of *Strawberry latent ringspot virus* (SLRSV) in the cultivar 'Raggiola')

In order to prevent the spread of dangerous pathogens (*Verticillium dahliae, Pseudomonas savastanoi* pv. *savastanoi)* and viruses in particular, remedies rely mainly on preventive measures such as the use of pathogen-tested propagative material. The main approach used to obtain, propagate and commercialize plants free from harmful pathogens is through phytosanitary selection and certification programs, which also encompass pomological selection for trueness to type and superior quality traits. In order to obtain pathogen-free material from infected trees, sanitation treatments such as heat therapy, meristem tip culture and micrografting, although still limited for their application for virus elimination in olive plants, can be applied.

A certification program is a procedure whereby single well-analysed candidate mother plants (nuclear stock plants) are used as sources of propagation material with a process of filiation. In this way, it is possible to provide growers with high quality (genetic and

sanitary) material. The certification scheme in general, and phytosanitary in particular, can be adopted either for worldwide spread varieties or for those locally distributed.

Phytosanitary Certification 109

the virus isolate, cultivar, season and year. Many plant species infected with ArMV, including olive trees, do not show any symptoms (Martelli et al., 2002). The virus has been reported in olive trees from Italy (Savino et al., 1979), Portugal (Martelli, 2011) Egypt, USA (Saponari & Savino, 2003), Turkey (Çağlayan et al., 2004), Syria (Alabdullah et al., 2005) and

*Cherry leaf roll virus (CLRV)* belongs to the family *Secoviridae*, genus *Nepovirus,* subgroup c. Even if it is classified as a *Nepovirus*, its transmission by nematodes has not yet been demonstrated to date, whereas it effectively occurs by pollen and, in some hosts, very efficiently by seed too. In olive plants, its transmission by means of pollen has not been demonstrated, but has been ascertained by seeds at the rate of 41% (Saponari et al., 2002). CLRV infects many herbaceous, shrubs and woody plants of genera: *Betula, Celtis, Cornus, Fagus, Juglans, Ligustrum, Olea, Populus, Ulmus, Rubus, Sambucus* and *Rheum*. The virus often induces symptoms in ash, birch, cherry, elderberry and walnut including delayed leaf development, chlorotic leaf streaks or spots, as well as dieback of branches or whole trees but it is symptomless in olive trees (Savino & Gallitelli, 1981). Its presence in olive trees was reported in Italy, Portugal, Spain (Martelli, 1999), then in Egypt, USA (Saponari & Savino, 2003), Turkey (Çağlayan et al., 2004), Syria (Alabdullah et al., 2005), Lebanon (Fadel et al., 2005) and recently in Croatia (Luigi et al., 2011), where it has been shown to have a negative

*Strawberry latent ringspot virus (SLRSV)* is an unassigned species in the *Secoviridae* family. It is transmitted by the nematode *X. diversicaudatum* and by seed in several species (Cooper, 1986), but in olive plants, these kinds of means of transmission have not been demonstrated. SLRSV infects strawberry and raspberry, mostly without symptoms but resulting in various degrees of mottle and decline in some cultivars. The virus was isolated for the first time from olive in cv. 'Corregiolo' in Italy (Savino et al., 1979) and later in Portugal (Henriques et al., 1992), Spain (Bertolini et al., 1998), Egypt, USA (Saponari & Savino, 2003), Turkey (Çağlayan et al., 2004), Lebanon (Fadel et al., 2005), Syria (Alabdullah et al., 2005), Croatia (Bjelis et al., 2007), Tunisia (Martelli, 2011) and Albania (Luigi et al., 2009). Small, pearshaped, puckered fruits with deformed kernels (bumpy fruits), narrow and twisted leaves, bushy growth and reduced crop were described in olive trees of cv. 'Ascolana tenera' affected by SLRSV (Marte et al., 1986). Similar symptoms were observed in cvs 'Negrinha' and 'Galega' in Portugal, associated with a severe reduced rooting ability of the cuttings (Henriques et al., 1992). Among 15 different olive cultivars reporting plants being affected by SLRSV in Portugal, only some showed symptoms (Henriques et al., 1992) in agreement with what was observed in Italy (Savino et al., 1979; Marte et al., 1986); no symptoms are apparently associated with SLRSV infections in Spain (Bertolini et al., 1998). Very interesting is the fact that previously, the 'Raggiola' and 'Frantoio' were considered different olive varieties due to morphological and agronomical dissimilarities. A relatively recent study showed that the two cultivars are genetically identical and that their differentiations are due to the constant presence of SLRSV in 'Raggiola' and the repeated SLRSV absence in 'Frantoio' (Fig. 1) (Ferreti et al., 2002). Rooting trials conducted to compare SLRSV-infected 'Raggiola' with virus-free 'Frantoio' showed that the virus does not influence the rooting

impact on olive fruit and virgin oil quality (Godena et al., 2012).

Lebanon (Fadel et al., 2005).

Each step of the propagation (descendent filiation) (Pre-basic, Basic and Certified material) must comply with the requirements that are intended to produce and maintain the selected material in the best growing conditions as specified by the enforced phytosanitary regulations. In particular, the sanitary status must be assessed following the officially recognized technical procedures, regarding the list of the target pathogens, type of sample, period of sampling and protocol for testing.

Phytosanitary selection requires the use of appropriate diagnostics protocols for pathogen detection. The difficulty in recognising and/or diagnosing virus-infected olive trees during field surveys imposes the use of laboratory tests in order to assess the absence of the target pathogens. Due to the lack of indicators for the biological assays and the unreliability of the ELISA test in olive, the application of molecular diagnostic techniques for viruses, fungi and bacteria detection became, in the recent past, critical for the assessment of the sanitary status of a given selected ecotype. These sensitive and reliable methods are absolutely necessary as they are at the basis of efficient and valid certification programs.

The increasing international demand for olive products, and therefore the expansion of olive crops, is stimulating the exchange of olive germplasm in new areas of the world, prompting for the adoption at European and International level of harmonised Certification Programs that reduce risks of pathogen dissemination and ensure the commercialisation of high quality propagative material and, consequently, guarantee high quality olive productions.
