Characterisation and epidemiology of Colletotrichum acutatum sensu lato(C. chrysanthemi) causing Carthamus tinctorius anthracnose

In 2012, Colletotrichum isolates were collected from field-grown safflower crops in central Italy from plants exhibiting typical anthracnose symptoms. Colletotrichum isolates were also collected from seed surfaces and from within seeds. The genetic variability of these isolates was assessed by a multilocus sequencing approach and compared with those from C. chrysanthemi and C. carthami isolates from different geographic areas and other C. acutatum s.l.-related isolates. Phylogenetic analyses reveal that all of the strains isolated from Carthamus tinctorius belong to the species described as C. chrysanthemi, while, all of the strains belonging to C. carthami had been isolated from Chrysanthemum spp. Phenotypic characterization was performed by assessing growth rates at different temperatures, morphology of colonies on PDA and the size of conidia. All C. chrysanthemi isolates from safflower had similar growth rates at different temperatures, comparable colony morphologies when grown on PDA and conidial sizes consistent with previously described C. chrysanthemi isolates. Pathogenicity tests were performed by artificially inoculating both seeds and plants and confirmed the seed-borne nature of this pathogen. When inoculated on plants, C. chrysanthemi caused the typical symptoms of anthracnose on leaves. This is the first record of this pathogen on Carthamus tinctorius in Italy, and it presents an updated characterisation of Colletotrichum isolates pathogenic to safflowers in Europe.