HomePlant DiseaseVol. 101, No. 12First Report of Alternaria alternata as the Causal Agent of Alternaria Bud and Blossom Blight of Olives PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Alternaria alternata as the Causal Agent of Alternaria Bud and Blossom Blight of OlivesC. S. Lagogianni, E. C. Tjamos, P. P. Antoniou, and D. I. TsitsigiannisC. S. LagogianniSearch for more papers by this author, E. C. TjamosSearch for more papers by this author, P. P. AntoniouSearch for more papers by this author, and D. I. Tsitsigiannis†Corresponding author: D. I. Tsitsigiannis; E-mail: E-mail Address: [email protected]http://orcid.org/0000-0003-2006-6106Search for more papers by this authorAffiliationsAuthors and Affiliations C. S. Lagogianni , Laboratory of Plant Pathology, Department of Crop Science, Agricultural University of Athens, 11855, Athens, Greece E. C. Tjamos , Hellenic Plant Clinic Center, 16673 Voula, Greece P. P. Antoniou D. I. Tsitsigiannis † , Laboratory of Plant Pathology, Department of Crop Science, Agricultural University of Athens, 11855, Athens, Greece. Published Online:13 Oct 2017https://doi.org/10.1094/PDIS-04-17-0527-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat A severe blight of buds and flowers in olive trees (Olea europaea L.) was observed in the Aitoloakarnania region, West-Central Greece, during the 2015 to 2017 growth seasons. Symptoms appeared in buds and expandable flowers of >100 trees cv. Kalamon in 30 olive groves (50 to 60% disease incidence). Necrotic buds and flowers appeared scattered in the tree, reaching up to 70% disease severity in some trees. Microscopic observations of dead buds and flower tissues showed abundant Alternaria-like conidia. Dead buds and dead flowers (50 each) were collected from 50 olive trees cv. Kalamon in December 2015, surface-sterilized in 0.5% NaClO for 10 min, rinsed with sterile ddH2O, immersed in 70% EtOH for 3 min, rinsed again with sterile ddH2O, dried in sterile filter paper, and finally placed in potato dextrose agar and in Rose-Bengal media. Plates were incubated at 25οC with a 12-h photoperiod for 5 days. Dark green fungal colonies with septate hyphae and conidia were consistently isolated from all diseased buds and flowers. Conidia were characteristic of Alternaria spp., brown with conidiophores in chains. Conidia of a representative isolate measured an average body length of 23.9 ± 1.1 (16.9 to 30.5) μm, an average body width of 9.4 ± 0.4 (7.0 to 12.0) μm, and the length-width ratio was 2.5 ± 0.2 (n = 60). The percentage of spores with beaks was 55% and presented 2.8 ± 0.9 (1 to 4) transverse septa and 0.5 ± 0.4 (0 to 1) vertical septa. The cell number of conidia was 5.5 ± 1.0. These morphological characteristics were comparable to those of A. alternata (Simmons 2007). To identify the fungus to species level, DNA from five single-spore isolates was extracted and the endopolygalacturonase (endoPG), Alternaria major allergen (Alta1), and ITS1-5.8-ITS2 genes were amplified and further sequenced using primers PG3/PG2b (Andrew et al. 2009), Alt-for/Alt-rev (Woudenberg et al. 2015), and ITS4/ITS5, respectively. BLAST analysis showed 99 to 100% identity to the type species A. alternata for all isolates and sequence data were submitted to GenBank (accession nos. KY923228 [AltPg-1], KY923227 [Alta1], and KY750255 [ITS1-5.8-ITS2]). Pathogenicity tests were carried out by spraying conidia suspensions (106 conidia/ml) of four different isolates on four branches (one branch/isolate) that included flowers, buds, stems, and leaves from a healthy 4-year-old olive tree cv. Kalamon or Koroneiki, in April 2015 (five replicate trees/cultivar). Three control plants of each cultivar were sprayed with sterilized distilled water (Berbegal et al. 2014). Plants were covered with transparent plastic bags for 10 days and trees were kept in a greenhouse at 20 to 25°C for 30 days under natural light conditions. Disease symptoms of necrotic blossoms and buds appeared in the infected trees of all isolates in both cultivars and were similar to those observed under natural infection in the region of Aitoloakarnania. The fungi were reisolated from dead buds and flowers as described before, confirming Koch’s postulates. Neither symptoms nor positive isolations were observed in control plants. Alternaria spp. are well known pathogens that infect a wide range of fruits (citrus, pomegranate, olive, pome fruits) (Basım et al. 2017), but they have never been observed in olive buds and flowers. For the disease reported here, we suggest the name “Alternaria bud and blossom blight of olives.” To the best of our knowledge, this is the first worldwide report of a disease caused by Alternaria spp. in buds and blossoms of olive trees.