In November 2019, a severe outbreak of fruit rot was observed in olive orchards in Crete, southern Greece. Symptoms appeared primarily on fruits and stalks, resembling those caused by anthracnose. Typical symptoms were fruit rot, shrinkage, and mummification, associated commonly with stalk discoloration and fruit drop. Disease incidence was estimated at up to 100% in some cases, and an unprecedented increase in olive oil acidity reaching up to 8% (percentage of oleic acid) in severely affected olive groves was recorded. Thirty-two olive groves were then surveyed, and samples of fruit, stalk, leaf, and shoot were collected. Visual, stereoscopic, and microscopic observations revealed several fungi belonging to the genera Alternaria, Botryosphaeria, Capnodium, Colletotrichum, Fusarium, and Pseudocercospora. Fungal infection in fruits was commonly associated with concomitant infestation by the olive fruit fly Bactrocera oleae along with increased air temperature and relative humidity conditions that prevailed in October and November 2019. Twenty representative fungal strains isolated from symptomatic fruits and stalks were characterized by morphological, physiological, and molecular analyses. By internal transcribed spacer regions of ribosomal DNA region and translation elongation factor 1-α gene sequencing analysis, these isolates were identified as Alternaria spp., A. infectoria, Botryosphaeria dothidea, Colletotrichum boninense sensu lato, Fusarium lateritium, F. solani species complex and Stemphylium amaranthi. Pathogenicity tests on punctured fruits revealed that all isolates were pathogenic; however, F. solani isolates along with B. dothidea were the most virulent, and wounds were necessary for efficient fungal infection. Moreover, as few as 10 spores of F. solani were sufficient to cause significant infection in punctured fruits. F. solani was also capable of infecting olive fruits in the presence of B. oleae, with no additional wounding, in artificial inoculation experiments. Moreover, it was capable of colonizing and affecting olive blossoms. Further analyses of olive oil extracted from fruits artificially inoculated with F. solani indicated a significant increase in oil acidity, K₂₃₂, K₂₇₀, and peroxide value, whereas total phenol content was significantly decreased. To the best of our knowledge, this is the first report of F. solani associated with olive fruit rot and olive oil degradation worldwide.

A three-year survey was conducted to estimate the incidence of grapevine trunk diseases (GTDs) in Greece and identify fungi associated with the disease complex. In total, 310 vineyards in different geographical regions in northern, central, and southern Greece were surveyed, and 533 fungal strains were isolated from diseased vines. Morphological, physiological and molecular (5.8S rRNA gene-ITS sequencing) analyses revealed that isolates belonged to 35 distinct fungal genera, including well-known (e.g., Botryosphaeria sp., Diaporthe spp., Eutypa sp., Diplodia sp., Fomitiporia sp., Phaeoacremonium spp., Phaeomoniella sp.) and lesser-known (e.g., Neosetophoma sp., Seimatosporium sp., Didymosphaeria sp., Kalmusia sp.) grapevine wood inhabitants. The GTDs-inducing population structure differed significantly among the discrete geographical zones. Phaeomoniella chlamydospora (26.62%, n = 70), Diaporthe spp. (18.25%, n = 48) and F. mediterranea (10.27%, n = 27) were the most prevalent in Heraklion, whereas D. seriata, Alternaria spp., P. chlamydospora and Fusarium spp. were predominant in Nemea (central Greece). In Amyntaio and Kavala (northern Greece), D. seriata was the most frequently isolated species (>50% frequency). Multi-genes (rDNA-ITS, LSU, tef1-α, tub2, act) sequencing of selected isolates, followed by pathogenicity tests, revealed that Neosetophoma italica, Seimatosporium vitis, Didymosphaeria variabile and Kalmusia variispora caused wood infection, with the former being the most virulent. To the best of our knowledge, this is the first report of N. italica associated with GTDs worldwide. This is also the first record of K. variispora, S. vitis and D. variabile associated with wood infection of grapevine in Greece. The potential associations of disease indices with vine age, cultivar, GTD-associated population structure and the prevailing meteorological conditions in different viticultural zones in Greece are presented and discussed.

Almond (Prunus dulcis) is an important crop for Greece grown on 15.130 ha in 2019. In September 2019, a severe stem canker disease was observed in 6-year-old trees of cv Marta grafted on the rootst...

A survey was conducted in olive orchards (Olea europaea L., cv Koroneiki) showing severe decline in Milatos and Ierapetra (Lasithi, Crete, Greece) in November 2017 and January 2019, respectively. Diseased trees exhibited wilting, yellowing of leaves, twig and branch dieback, and internal discoloration of vascular tissue. Insect infestations were commonly associated with these symptoms. A yeast-like fungus was consistently isolated from discolored vessels previously surface-disinfested with 95% ethanol, on acidified potato dextrose agar (APDA). The fungus yielded several dark brown to black, globose to oval pycnidia with dimensions 120–330 × 90–300 μm (average 179.6 × 143.9 μm), after 25 days of growth on APDA. Emerging colonies were transferred to new PDA and their growth rate was 2.21 mm/day at 24 °C in the dark. The sparse aerial mycelium was initially white, turning into beige-pinkish in the centre after 21 days of growth on PDA. Microscopic observations revealed hyaline, smooth, ampulliform conidiophores, bearing conidia solitary or in slimy heads. Conidia were 1-celled, hyaline, smooth, subcylindrical with obtuse ends, 1.25–5.75 × 0.75–2.00 μm (average 3.12 × 1.16 μm) in size. Light to dark brown pycnidia, semi-immersed in PDA, with dimensions 150–490 × 90–320 μm (average 297.7 × 231.0 μm) were evident in 3-week-old cultures. Colony morphology and microscopic features were similar to Pseudophaeomoniella oleae (Crous et al. 2015). DNA from two representative isolates (EML1 and DRAGVR1) was extracted and their internal transcribed spacer region (ITS) of ribosomal DNA, actin (ACT) and translation elongation factor 1-alpha (TEF1-α) genes were amplified using the primer pairs ITS1/ITS4 (White et al. 1990), ACT-512F/ACT-783R and EF1-728F/EF1-986R (Carbone and Kohn 1999), respectively. PCR products were sequenced and deposited in GenBank (accession Nos. MZ854242-MZ854243, OK143463-OK143464 and OK143465-OK143466). BLAST search revealed high similarity to GenBank sequences of the ex-type strain of P. oleae for ITS (≥99.50%, NR_137966.1 and KP635972.2), ACT (100%, KP635974.1), and TEF-1a (98.32%, KP635968.1). Based on morphology and phylogenetic analysis of the ITS region, the fungus was identified as P. oleae. Ten 3-year-old olive trees of each of the cvs Amfissis and Koroneiki were artificially inoculated by drilling a 3-mm-diameter hole into the trunk and injecting 50 μl of a 1 × 107 ml-1 conidia suspension of the isolate DRAGVR1 (Markakis et al. 2017). Another ten trees of each cv treated similarly with sterilized distilled water served as controls. Potted trees were kept under ambient conditions. Fourteen months post inoculation, longitudinal and transverse sections of inoculated trunks revealed wood discoloration extending above and below the inoculation point in both cultivars, whereas no leaf symptoms were observed. P. oleae was steadily re-isolated from symptomatic wood tissue and identified by colony morphology. Neither symptoms nor positive isolations were observed in controls. To our knowledge, this is the first report of wood streaking and decay caused by P. oleae in olive trees in Greece. Although the fungus has been isolated previously from decayed olive trees showing vascular wilt in Italy (Crous et al. 2015), this is the first experimental evidence of the pathogenic potential of the species on olive trees worldwide. This disease could potentially be an increasing problem in olive tree growing areas and result in severe crop losses. Hence, effective management practices should be investigated and applied.

A three-year survey was conducted to estimate the incidence of grapevine trunk diseases (GTDs) in Greece and identify fungi associated with the disease complex. In total, 310 vineyards in different geographical regions in northern, central, and southern Greece were surveyed, and 533 fungal strains were isolated from diseased vines. Morphological, physiological and molecular (5.8S rRNA gene-ITS sequencing) analyses revealed that isolates belonged to 35 distinct fungal genera, including well-known (e.g. Botryosphaeria sp, Diaporthe spp., Eutypa sp., Diplodia sp., Fomitiporia sp., Phaeoacremonium spp., Phaeomoniella sp.) and lesser-known (e.g. Neosetophoma sp., Seimatosporium sp., Didymosphaeria sp., Kalmusia sp.) grapevine wood inhabitants. GTDs-inducing population structure differed significantly among the discrete geographical zones. Phaeomoniella chlamydospora (26.62%, n=70), Diaporthe spp. (18.25%, n=48) and F. mediterranea (10.27%, n=27) were the most prevalent in Heraklion, whereas D. seriata, Alternaria spp., P. chlamydospora and Fusarium spp. were predominant in Nemea (central Greece). In Amyntaio and Kavala (northern Greece), D. seriata was the most frequently isolated species (>50% frequency). Multi-genes (rDNA-ITS, LSU, tef1-α, tub2, act) sequencing of selected isolates, followed by pathogenicity tests revealed that Neosetophoma italica, Seimatosporium vitis, Didymosphaeria variabile and Kalmusia variispora caused wood infection with the former being the most virulent. To the best of our knowledge, this is the first report of N. italica associated with GTDs worldwide. This is also the first record of K. variispora, S. vitis and D. variabile associated with wood infection of grapevine in Greece. The potential associations of disease indices with vine age, cultivar, GTD-associated population structure and the prevailed meteorological conditions in different viticultural zones in Greece are presented and discussed.

Verticillium wilt caused by the soil-borne fungus Verticillium dahliae causes severe losses to a broad range of economically important crops worldwide. Chemical disease management is ineffective; thus, alternative control strategies are needed. Olive-producing countries face the challenge of managing olive mill wastewater (OMW) in an environmentally friendly and agronomically beneficial manner. The proper use of OMW supported by scientific research has been proposed as a valuable means for successful disease management. In this respect, we tested whether soil application of raw OMW can protect vegetable crops against V. dahliae and investigated the potential disease-suppressive mechanisms. OMW inhibited significantly fungal growth, sporulation, hyphae width, and conidial and microsclerotial germination in vitro, and these effects were dose-dependent. Moreover, the addition of OMW in the soil provided sufficient protection of eggplant and tomato against V. dahliae in planta. The high OMW-conferred protection of eggplant was gradually decreased, possibly due to the decreased phenolic content in OMW over time. Bioassays with sterilized soil substrate and OMW, along with isolated microbial strains, revealed that soil- and OMW-originated microbes had no role in disease suppression. Moreover, split-root set-ups suggested a non-systemic OMW-induced resistance mechanism. Root-drench application of OMW in eggplant and tomato plants did not cause significant alterations in the structure of the plant microbiome that could be associated with disease suppressiveness.