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Vineyard surveys of Corinth raisin cultivar carried out in the Peloponnese region of Greece during 2002 and of wine-producing grape cultivars (Cabernet Sauvignon and Grenache Rouge) on the island of Rhodes, Greece, during 2003, demonstrated the occurrence of various Aspergillus spp. in berries of bunches at harvest. Aspergillus niger and A. carbonarius were predominantly isolated from sampled berries. Although the prevailing Aspergillus spp. isolates belonged mainly to A. niger aggregate, isolates of A. carbonarius were by far the most efficient Ochratoxin A (OTA) producers as revealed by the enzyme-linked immunosorbent assay test. This study provides the first evidence concerning the composition of Aspergillus populations in raisin and wine-producing vineyards and offers convincing data for their ability to produce various levels of OTA in Corinth raisins and wine-producing grapes in Greece. Furthermore, it demonstrates that chemical applications with the fungicide Switch, especially under low to intermediate Aspergillus infection of vineyards, could both significantly reduce the occurrence of OTA-producing Aspergillus spp. and restrict sour rot severity. In contrast, vineyard applications with the fungicides Carbendazim or Chorus were ineffective in controlling the fungus in Corinth raisin cultivar. U. S.

Verticillium wilt is the most serious olive disease worldwide. The olive-infecting Verticillium dahliae pathotypes have been classified as defoliating (D) and nondefoliating (ND), and the disease is mainly controlled in olive orchards by using resistant or tolerant cultivars. Limited information is available about the nature of resistance in most of the olive cultivars. In the present study, the phenolic responses of the susceptible to V. dahliae olive cv. Amfissis and the resistant cv. Koroneiki upon D and ND V. dahliae infection were monitored in relation to the fungal DNA levels in the vascular tissues with the purpose to explore the defense mechanisms of olive trees against V. dahliae. Quantitative polymerase chain reaction revealed that the decrease in symptom severity shown in Koroneiki trees was associated with significant reduction in the growth of both V. dahliae pathotypes in the vascular tissues compared with Amfissis. In Koroneiki trees, the levels of o-diphenols and verbascoside were positively associated with the DNA levels of the D and ND pathotypes. In addition, a positive association was observed between the levels of verbascoside and the fungal DNA level in Amfissis trees, whereas a negative association was revealed between the fungal DNA level and the total phenols and oleuropein content in both cultivars. The levels of verbascoside were clearly higher in Koroneiki trees compared with Amfissis trees, indicating for the first time in the literature the involvement of verbascoside in the defense mechanism of olive trees against V. dahliae.

Control of verticillium wilt of olive currently depends on preventive measures. Since systemic fungicides are unable to prevent or control the disease, its control should primarily be based on cultural methods, including irrigation systems which restrict dissemination of Verticillium dahliae propagules by irrigation water and avoidance of intercropping with hosts susceptible to V. dahliae. Since leaves from affected olive trees contribute, through formation of microsclerotia, to the inoculum in the soil, pruning should be practised prior to branch defoliation. As for resistant olive rootstocks or cultivars, promising verticillium‐wilt resistance has been found in two rootstocks selected in California (US). However, these have to be tested under local conditions before they can be released to Mediterranean growers, while further search for other resistant rootstocks is needed. Soil solarization applied to individual diseased trees in established olive groves could substantially contribute to recovery or long‐lasting symptom remission in the treated trees. This effect is mainly attributed to the decrease or eradication of V. dahliae microsclerotia in the treated soil but also to heat‐tolerant fungal antagonists of the pathogen. Using herbicides to control weeds, and limiting soil rotovation, can restrict symptom development. Biological control can also be considered as a promising trend in controlling the disease by searching, testing and exploiting potential fungal or bacterial antagonists.

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Verticillium wilt is the most serious olive disease in the Mediterranean countries and worldwide. The most effective control strategy is the use of resistant cultivars. However, limited information is available about the level and source of resistance in most of the olive cultivars and there are no published data using microsclerotia, the resting structures of Verticillium dahliae, as the infective inoculum. In the present study, we correlated symptomatology and the presence of the fungus along with the DNA relative amount (molecules μl −1 ) of a defoliating (D) and a non-defoliating (ND) V. dahliae strain in the susceptible cv. Amfissis and the tolerant cvs Kalamon and Koroneiki, as quantified by the Real-Time QPCR technology. The viability of the pathogen in the plant tissues was confirmed by isolating the fungus on PDA plates, while symptom assessment proved the correlation between the DNA relative amount of V. dahliae in plant tissues and cultivar susceptibility. It was further demonstrated that the D and ND strains were present at a significantly higher level in cv. Amfissis than in cvs Kalamon and Koroneiki. It was finally observed that the relative amount of the pathogen in roots was lower than in stems and shoots and declined in plant tissues over time. These data constitute a valuable contribution in evaluating resistance of olive cultivars or olive root-stocks to V. dahliae pathotypes.