Diversity of Colletotrichum Species Associated with Olive Anthracnose Worldwide

Abstract

Olive anthracnose caused by <i>Colletotrichum</i> species causes dramatic losses of fruit yield and oil quality worldwide. A total of 185 <i>Colletotrichum</i> isolates obtained from olives and other hosts showing anthracnose symptoms in Spain and other olive-growing countries over the world were characterized. Colony and conidial morphology, benomyl-sensitive, and casein-hydrolysis activity were recorded. Multilocus alignments of ITS, TUB2, ACT, CHS-1, HIS3, and/or GAPDH were conducted for their molecular identification. The pathogenicity of the most representative <i>Colletotrichum</i> species was tested to olive fruits and to other hosts, such as almonds, apples, oleander, sweet oranges, and strawberries. In general, the phenotypic characters recorded were not useful to identify all species, although they allowed the separation of some species or species complexes. ITS and TUB2 were enough to infer <i>Colletotrichum</i> species within <i>C. acutatum</i> and <i>C. boninense</i> complexes, whereas ITS, TUB2, ACT, CHS-1, HIS-3, and GADPH regions were necessary to discriminate within the <i>C. gloesporioides</i> complex. Twelve <i>Colletotrichum</i> species belonging to <i>C. acutatum</i>, <i>C. boninense</i>, and <i>C</i>. <i>gloeosporioides</i> complexes were identified, with <i>C. godetiae</i> being dominant in Spain, Italy, Greece, and Tunisia, <i>C. nymphaeae</i> in Portugal, and <i>C. fioriniae</i> in California. The highest diversity with eight <i>Colletotrichum</i> spp. was found in Australia. Significant differences in virulence to olives were observed between isolates depending on the <i>Colletotrichum</i> species and host origin. When other hosts were inoculated, most of the <i>Colletotrichum</i> isolates tested were pathogenic in all the hosts evaluated, except for <i>C. siamense</i> to apple and sweet orange fruits, and <i>C. godetiae</i> to oleander leaves.