*3.1.2. Cyanidine*

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

epicarp protect the fruit against olive fly ovideposition (Iannotta et al., 2002).

the same fruit (Girolami et al., 1981; Lo Scalzo et al., 1994). Oleuropein acts by inhibiting the development of olive fly immature stages, especially eggs and first instar larvae during the early ripening period (Iannotta et al., 2002). The higher concentration of oleuropein in the epicarp than in the mesocarp may be due to the biological function of oleuropein in drupe protection against pests (Soler-Rivas et al., 2000). In fact, the epicarp is the interface between the outer environment and the inner olive fruit. Therefore, high levels of oleuropein in the

Moreover, the defence response of fruits damaged both by pathogens and mechanical means, is mediated by β-glucosidase; this enzyme hydrolyses the oleuropein, producing highly reactive aldehyde molecules. Olive cultivars with different levels of enzyme activity have differing degrees of susceptibility to the olive fly. This may be related to the ability of the β-glucosidase to produce highly reactive aldehyde molecules in damaged tissues. A strong peroxidase activity is thereafter detected as a consequence of damage (Spadafora et al., 2008). Results obtained by Iannotta et al. (2001) showed that five cultivars (Bardhi i Tirana, Carboncella di Pianacce, Gentile di Chieti, Kokermadh i Berat, and Nociara) with high levels of drupe oleuropein (31.18 – 36.60 g kg-1) had low levels of infestation (lower than 10%). When oleuropein content decreases, a corresponding increase in the amount of damage caused by olive flies occurs. In the same cultivars, Iannotta et al. (2001) found that the percentage of sterile oviposition stings ranged from 25.0 to 27.5%. Similar results were also observed for cultivars Sant'Agostino, Leccino, and partially Frantoio (Basile et al., 2006). Sterile sting numbers and oleuropein content are inversely proportional to infestation (Iannotta et al., 2001). The role of oleuropein in the inhibition of the development of olive fly immature stages has been shown by performing a comparison between untreated olive samples and samples treated with oleuropein belonging to the cv. Carolea. The cultivar Carolea was chosen because it is susceptible to the olive fly. After ten days, infestation levels were 31% and 65%, respectively, in the oleuropein-treated and non-treated samples (Iannotta et al. 2002). The concentration of oleuropein is greater in the epicarp rather than in the mesocarp during the entire ripening process, except in the case of cvs. Gentile di Chieti and Picholine (Iannotta et al., 2002, 2007a). In these varieties, there is a slightly lower content of oleuropein in the epicarp during the early ripening period. In another study no correlation was observed between infestation and oleuropein content (Iannotta et al., 2006a). In fact, olive fly infestation may be different on the same olive cultivar under different environmental conditions (Fontanazza, 2000) inasmuch as the oleuropein content might be affected by climatic trend (Iannotta et al., 2006a). In a study performed in 2005 in an experimental field located on the Ionian coast of Calabria (Southern Italy), it was observed that cv Cellina di Nardò was the least infested by the olive fly in terms of total infestation (17.67%). In contrast, cvs. Ascolana tenera and Nostrana di Brisighella were the most damaged attaining percentages of total infestation at 56.33% and 57.67%, respectively (Iannotta et al., 2006a). This difference is presumably related also to fruit size (Daane and Johnson, 2010). In fact, Cellina di Nardò has relatively small fruits compared to Ascolana tenera and Nostrana di Brisighella. In addition, it has been shown that small-fruit cultivars

Cyanidine occurs in olive fruits (Servili et al., 1999) and an increase of cyanidine content at the end of the maturation stages of the olive fruit, as a consequence of hydrolytic processes, was found (Vinha et al., 2005). On the reasons of different genotype behavior concerning the susceptibility to olive fly attacks, the direct influence of cyanidine in the drupes could be, in effect, supposed. It is evident in cvs. Cellina di Nardò, Nolca and Termite di Bitetto which register high value of cyanidine, increasing during the season (Iannotta et al., 2006b). When investigated genotypes are cultivated in the same pedoclimatic conditions and samples obtained from them are collected in the same ripening times, it is possible attribute the differences, concerning cyanidine amount, to a strong influence of the different investigated genotypes genetic diversity. It has been observed that the completely pigmented drupes are not very recognizable by *B. oleae* females determining considerable difficulties for their ovideposition (Caleca, pers. comm.).

A role played by cyanidine in resistance to herbivores was additionally assessed (Harborne and Williams, 1998). Significant differences were found among cultivars in relation to active and total infestations and cyanidine content (Iannotta et al., 2006a). Cultivars Ascolana tenera and Nostrana di Brisighella had the highest level of active infestation (34.33% and 32.33%, respectively) while cv. Cellina di Nardò was the least infested (9.83%). In addition, cvs. Frantoio, Gordal sevillana, Koroneiki, Nera di Cantinelle, Nolca, Ogliarola garganica, and Tonda di Strongoli showed low levels of susceptibility to olive fly (lower than 15%). Cultivars Cellina di Nardò, Nolca, and Termite di Bitetto had higher levels of cyanidine than other cultivars in the study and had low levels of infestation.

In a study undertaken in 2005 in an experimental field located on the Ionian coast of Calabria (Southern Italy), Iannotta et al. (2007a) found the lowest susceptibility to olive fly attack for cvs Tonda nera dolce and Bardhi i Tirana (6.67% and 13.50%, respectively). On the contrary, cvs. Carolea, Cassanese, Carboncella di Pianacce, Gentile di Chieti, Giarraffa, Nocellara del Belice, Nociara and Picholine were susceptible with a mean percentage of active infestation ranging from 22.17 to 29.83%. The presence of cyanidine in the first

ripening period only for cv. Tonda nera dolce suggests a possible role in determining the lowest level of active infestation observed.

Susceptibility of Cultivars to Biotic Stresses 103

resistance sources may represent an effective means for olive crop management. In fact, using olive cultivars with low susceptibility to olive fly may represent an effective strategy for

*Agricultural Research Council - Olive Growing and Oil Industry Research Centre, Rende (CS), Italy* 

We thanks Veronica Vizzarri, Tiziana Belfiore, Maria Elena Noce, Luigi Perri and all the other colleagues involved in field and laboratory works and that allow us to write this contribute. Financial support was provided by the Italian Ministry of Agriculture, Food and Forestry Policy through the project GERMOLI "Salvaguardia e valorizzazione del

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Amiot, M.-J.; Fleuriet, A. & Macheix, J.-J. (1989). Accumulation of oleuropein derivatives

Baidez, A.G.; Gomez, P.; Del Rio, J.A. & Ortuno, A. (2007). Disfunctionality of the xylem in *Olea europaea* L. plants associated with the infection process by *Verticillium dahliae* Kleb. role of phenolic compounds in plant defense mechanism. *Journal of Agricultural and Food* 

Basile, B.; Romano, R.; Garonna, A.P.; Forlani, M. & Rao, R. (2006). Preliminary study of the susceptibility of different olive cultivars to olive fruit fly [Bactrocera oleae (Gmel.)]. *Proceedings of the Second International Seminar on "Biotechnology and Quality of Olive tree Products around the Mediterranean basin", Olivebioteq, Marsala-Mazara del Vallo 5-10* 

Bisignano, G.; Tomaino, A.; Lo Cascio, R.; Crisafi, G.; Uccella, N. & Saija, A. (1999). On the in vitro antimicrobial activity of oleuropein and hydroxytyrosol. *J. Pharm. Phrmacol.*,

Cirio, U. (1971). Reperti sul meccanismo stimolo-risposta nell'ovideposizione del *Dacus oleae* 

Colella, C.; Miacola, C.; Amenduni, M.; D'Amico, M.; Bubici, G. & Cirulli, M. (2008). Sources of verticillium wilt resistence in wild olive germplasm from the Mediterranean region.

Daane, K.M. & Johnson, M.W. (2010). Olive fruit fly: managing an ancient pest in modern

organic and integrated pest management, eliminating or decreasing pesticides inputs.

**Author details** 

**Acknowledgement** 

**4. References** 

Nino Iannotta and Stefano Scalercio

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Studies on cultivars Bardhi i Tirana, Carolea and Tonda nera dolce (Iannotta et al., 2007a) corroborate results obtained in previous investigations. Cultivars Bardhi i Tirana and Carolea were selected because they have low and high levels of susceptibility, respectively, to olive fly whilst cultivar Tonda nera dolce was selected because it shows high levels of cyanidine. Differences were found among the three cultivars in relation to active and total infestations and oleuropein and cyanidine contents. The lowest percentages of active and total infestations were observed on cv. Tonda nera dolce (8.62% and 20.12, respectively), while cv. Carolea had the most damage (29.00% and 49.38%, respectively). Cultivar Bardhi i Tirana showed intermediate values of active and total infestations. The low susceptibility found for cv Bardhi i Tirana, although greater than the susceptibility showed by cv Tonda nera dolce, might be due to the highest oleuropein content observed. The content of cyanidine in cv. Tonda nera dolce might be responsible for the lowest susceptibility found.

Cyanidine probably acts by giving olive fruits a dark colour during the early ripening stages. This may confuse female olive flies in drupe recognition resulting in a decrease in oviposition. This hypothesis is supported by the evidence that in herbivorous diurnal insects, visual cues may play an important role in the location of host plants and essential resources, such as food, mating, and oviposition sites (Prokopy and Owens 1983). This situation is very common for frugivorous Tephritid flies that feed and oviposit on fruits (Katsoyannos, 1989; Fletcher and Prokopy, 1991; Diaz-Fleischer et al., 2000; Prokopy and Papaj, 2000). A laboratory experiment investigating the effect of fruit colour on attracting olive fruit fly females was carried out by Katsoyannos et al. (1985). In this study, females were left to select for oviposition sites among hollow, hemispheric, ceresin wax domes of different colours. Yellow and orange domes were preferred for oviposition compared to domes of other colours. Red, blue, black, and white domes were the least preferred. Red, blue, and black correspond to the colour of ripening olives reached during the maturation stages. Fruit colour is genetically determined in some cultivars and is related to the content of anthocyanins. Olive fly females prefer green olives for oviposition compared to red and black olives (Cirio, 1971; Rizzo and Caleca, 2006).

The high content of phenolic compounds found in several cultivars is a resource in olive germplasm. Field researches demonstrated that a high content of phenolic compounds is related to low susceptibility to olive fly attacks and other parasites. Therefore, the planting of genotypes containing high amounts of these compounds may greatly contribute to a significant reduction of pesticides inputs. In addition, the presence of phenolic compounds in olive fruits is also associated with various benefits for human health deriving from high quality olive oil intake. Therefore, the conservation of olive intraspecific biodiversity preserves sources of genetic resistance to various pests. To preserve olive germplasm biodiversity in accordance with CAP directives and minimize pesticide use diversifying agronomic practices are strongly related. Strategic *B. oleae* control is thus a priority for safeguarding both environmental integrity and consumer health. The identification of genetic resistance sources may represent an effective means for olive crop management. In fact, using olive cultivars with low susceptibility to olive fly may represent an effective strategy for organic and integrated pest management, eliminating or decreasing pesticides inputs.
