First report of Colletotrichum nymphaeae on olive in Italy.
Olive anthracnose is one of the most important diseases of olive worldwide. Among the Colletotrichum species associated to the disease, some in the complexes C. acutatum and C. gloeosporioides have been reported as the most frequent in Italy. During the 2017 season, severe losses were reported in several (18) olive orchards (approximately 30 ha) located in the districts of San Daniele, Friuli Venezia Giulia, one of the northernmost olive growing areas in Italy. Drupes from cultivars Leccino and Leccio del Corno, at fruit size approximately 10% of final size (July), showed no symptoms or small, dark-brown rot lesion in the flesh; sometimes, peduncle was chlorotic, then necrotic, causing an easy detachment of the fruitlets. Symptomatic and asymptomatic fruits fell to the ground, determining a premature fruit drop of 70 to 80% of the fruit. Based on the results of morphological observations, molecular investigations (sequence analysis of the internal transcribed spacer, the 28S ribosomal RNA and partial sequence of β-tubulin regions) and pathogenicity tests, the causal agent was identified as Colletotrichum nymphaeae. This fungus has been previously reported to cause severe anthracnose on olive in Portugal and on multiple hosts in diverse parts of the world. C. acutatum sensu stricto and Colletotrichum godetiae have been reported as dominant species of olive anthracnose in Italy. This is thought to be the first report of C. nymphaeae causing olive anthracnose in Italy.