High fungal species diversity in association with woody ornamental plants: Colletotrichum as a case study

V. Guarnaccia, I. Martino, G. Gilardi, A. Garibaldi, M.L. Gullino
Woody ornamental plants represent an important part of the agriculture sector. The increasing of woody ornamentals global movement has led likewise to the spread of pest and pathogens in new areas. Diseases affecting these crops are emerging mainly due to the intercontinental movement of plant materials despite the phytosanitary regulations. Moreover, the climate change can promote favorable conditions for pathogens development and diffusion in temperate regions. In Italy, several fungal genera have been reported as pathogens of woody ornamental in nurseries and public or private gardens. Emerging anthracnose diseases have been observed during the last decade associated with woody ornamental hosts. Thus, this study aimed to explore the occurrence, diversity and pathogenicity of Colletotrichum spp. Surveys were carried out during the 2014-2019 period in Piedmont, northern Italy. The work considered a total of 21 Colletotrichum strains placed at the culture collection of AGROINNOVA (University of Torino). A multi-locus phylogeny was established based on three genomic loci (gapdh, act and tub2). The aggressiveness of representative isolates was tested. Colletotrichum fioriniae was found in association with Salvia leucantha, oregano and Mahonia aquifolium. Colletotrichum fructicola was found on leaf spot of Ceanothus thyrsiflorus, Hydrangea paniculata, Liquidambar styraciflua, and S. greggii. Colletotrichum grossum and C. kahawae were isolated from Rhyncospermum jasminoides and Liquidambar styraciflua, respectively. Colletotrichum nigrum and C. bryoniicola were isolated from S. greggii and S. nemorosa, respectively. All the tested strains were pathogenic and reproduced symptoms identical to those observed at the beginning of the survey. The present study improves our understanding of Colletotrichum species and it underlines the importance of a polyphasic approach to provide a correct species-level identification within this genus. Furthermore, this work provides useful information for an effective disease management program and for the development of species-specific diagnostic tools.
Guarnaccia, V., Martino, I., Gilardi, G., Garibaldi, A. and Gullino, M.L. (2021). High fungal species diversity in association with woody ornamental plants: Colletotrichum as a case study. Acta Hortic. 1331, 293-302
DOI: 10.17660/ActaHortic.2021.1331.39
woody ornamentals, leaf spot, multi-locus sequence typing, pathogenicity

Acta Horticulturae