Species Diversity in Colletotrichum Causing Anthracnose of Aromatic and Ornamental Lamiaceae in Italy

Species of Colletotrichum are considered important plant pathogens, saprobes, and endophytes on a wide range of host plants. In Italy, several Colletotrichum species have been reported in glasshouse environments. In this study, we have explored the occurrence, diversity, and pathogenicity of Colletotrichum spp. associated with aromatic and ornamental plants belonging to the Lamiaceae family. Surveys were carried out during the 2011–2018 period in Liguria and Piedmont, Italy. A total of 19 Colletotrichum isolates were collected from symptomatic leaves and seeds of Ocimum basilicum (basil), Origanum vulgare (oregano) and different Salvia spp. A multi-locus phylogeny was established based on the basis of four genomic loci (ITS, GAPDH, ACT and TUB2). The aggressiveness of selected, representative isolates were tested. Colletotrichum isolates were identified as being members of three major species complexes: C. acutatum, C. destructivum, and C. gloeosporioides. Colletotrichum fioriniae, C. bryonicola, and C. fructicola were found in association with leaf lesions on Salvia leucantha, S. nemorosa, and S. greggii, respectively. Colletotrichum nigrum was isolated from twig lesions of S. greggii. Moreover, C. fioriniae and C. ocimi were found to be responsible for causing leaf anthracnose of oregano and basil, respectively. All the tested isolates were pathogenic and reproduced identical symptoms to those observed in commercial glasshouses. The present study improves our understanding of Colletotrichum species associated with several hosts belonging to the Lamiaceae family, which are cultivated extensively throughout Italy for different purpose, and provides information that may be useful for an effective disease management program.