Diversity of Colletotrichum Species Associated with Olive Anthracnose Worldwide

Abstract

Olive anthracnose caused by Colletotrichum species causes dramatic losses of fruit yield and oil quality worldwide. A total of 185 Colletotrichum 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 Colletotrichum 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 Colletotrichum species within C. acutatum and C. boninense complexes, whereas ITS, TUB2, ACT, CHS-1, HIS-3, and GADPH regions were necessary to discriminate within the C. gloesporioides complex. Twelve Colletotrichum species belonging to C. acutatum, C. boninense, and C. gloeosporioides complexes were identified, with C. godetiae being dominant in Spain, Italy, Greece, and Tunisia, C. nymphaeae in Portugal, and C. fioriniae in California. The highest diversity with eight Colletotrichum spp. was found in Australia. Significant differences in virulence to olives were observed between isolates depending on the Colletotrichum species and host origin. When other hosts were inoculated, most of the Colletotrichum isolates tested were pathogenic in all the hosts evaluated, except for C. siamense to apple and sweet orange fruits, and C. godetiae to oleander leaves.

Molecular Characterization, Pathogenicity and Biological Characterization of Colletotrichum Species Associated with Anthracnose of Camellia yuhsienensis Hu in China

“…yuhsienensis, and the same symptoms occurred, confirming Koch's postulates (Figure 1C,D). All of the diseased leaves had irregular grayish brown spots with dark brown edges and dark brown undersides, similar to previous reports [38,39]. Ca.…”

Characterization of Colletotrichum Isolates Causing Colletotrichum Dieback of Citrus in California

“…Other authors suggested that this discrepancy may be due, at least partially, to differences in pathogenicity among isolates of the same species (Riolo et al 2021). Isolates of C. gloeosporioides associated with anthracnose in olive have been characterized by high variability in terms of aggressiveness (Schena et al 2014;Moral et al 2021). Because no intraspecific variability was observed among the isolates included in our study, more experiments are needed to explain dissimilar reports on the pathogenicity of pathogens that cause Colletotrichum dieback of citrus.…”

“…The Colletotrichum species also differed in the number of conidia produced on PDA. The importance of this characteristic for the identification of Colletotrichum species is limited, although has been used in fitness comparison studies (Moral et al 2021;Forcelini et al 2018). Relative growth rates in culture media can be used also to distinguish Colletotrichum species (Cai et al 2009;Sutton 1992;Velho et al 2015).…”

“…The phylogenetic analysis also supported the classification of fungal isolates made based on published descriptions. Other Colletotrichum species causing the same disease have been separated according to morphological characteristics (Moral et al 2021). Given the low number of species causing Colletotrichum dieback in California citrus, this criterion could be relevant.…”

“…Finally, 5-µl drops of the spore suspensions were mounted in microscope slides and the size of 100 conidia was examined using a Leica compound microscope (Leica DM2000 LED Microscope, Wetzlar, Germany). The length and width of each conidium were measured, and their volume was calculated according to Moral et al (2021). The entire experiment was conducted twice with three replicates per isolate.…”