Identification, prevalence and pathogenicity of Colletotrichum species causing anthracnose of Capsicum annuum in Asia

Dilani D De Silva,Johannes Z Groenewald,Orarat Mongkolporn,Pedro W Crous,Paul W J Taylor,Peter K Ades,Andi Nasruddin

doi:10.1186/s43008-019-0001-y

Dilani D De Silva, Johannes Z Groenewald + Show 5 more

Open Access

https://doi.org/10.1186/s43008-019-0001-y

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Abstract

Anthracnose of chili (Capsicum spp.) causes major production losses throughout Asia where chili plants are grown. A total of 260 Colletotrichum isolates, associated with necrotic lesions of chili leaves and fruit were collected from chili producing areas of Indonesia, Malaysia, Sri Lanka, Thailand and Taiwan. Colletotrichum truncatum was the most commonly isolated species from infected chili fruit and was readily identified by its falcate spores and abundant setae in the necrotic lesions. The other isolates consisted of straight conidia (cylindrical and fusiform) which were difficult to differentiate to species based on morphological characters. Taxonomic analysis of these straight conidia isolates based on multi-gene phylogenetic analyses (ITS, gapdh, chs-1, act, tub2, his3, ApMat, gs) revealed a further seven known Colletotrichum species, C. endophyticum, C. fructicola, C. karsti, C. plurivorum, C. scovillei, C. siamense and C. tropicale. In addition, three novel species are also described as C. javanense, C. makassarense and C. tainanense, associated with anthracnose of chili fruit in West Java (Indonesia); Makassar, South Sulawesi (Indonesia); and Tainan (Taiwan), respectively. Colletotrichum siamense is reported for the first time causing anthracnose of Capsicum annuum in Indonesia and Sri Lanka. This is also the first report of C. fructicola causing anthracnose of chili in Taiwan and Thailand and C. plurivorum in Malaysia and Thailand. Of the species with straight conidia, C. scovillei (acutatum complex), was the most prevalent throughout the surveyed countries, except for Sri Lanka from where this species was not isolated. Colletotrichum siamense (gloeosporioides complex) was also common in Indonesia, Sri Lanka and Thailand. Pathogenicity tests on chili fruit showed that C. javanense and C. scovillei were highly aggressive, especially when inoculated on non-wounded fruit, compared to all other species. The existence of new, highly aggressive exotic species, such as C. javanense, poses a biosecurity risk to production in countries which do not have adequate quarantine regulations to restrict the entry of exotic pathogens.

Highlights

Colletotrichum is one of the most important genera of plant pathogenic fungi with many of the 200 plus species known to cause disease in plant crops worldwide (Udayanga et al 2013; Marin-Felix et al 2017)
Morphological characters cannot differentiate many of the species with straight conidia, especially those in the acutatum and gloeosporioides complexes that are pathogens of chili, and multigene phylogenetic analyses are required for proper identification of these species (De Silva et al 2017a)
Colletotrichum truncatum was found in the collections from Indonesia, Malaysia, Sri Lanka and Thailand (Fig. 6)

Summary

Introduction

Colletotrichum is one of the most important genera of plant pathogenic fungi with many of the 200 plus species known to cause disease in plant crops worldwide (Udayanga et al 2013; Marin-Felix et al 2017). Colletotrichum species causing anthracnose of chili in Asia were previously identified as C. acutatum (straight conidia with acute ends), C. gloeosporioides (straight conidia with obtuse ends) and C. truncatum (falcate conidia) (Than et al 2008, Mongkolporn et al 2010,). With the implementation of multigene phylogenetic analyses, C. acutatum was demonstrated to be a species complex (acutatum complex) composed of 34 closely related species (Marin-Felix et al 2017), with seven species identified as causing anthracnose in chili (Mongkolporn and Taylor 2018). C. gloeosporioides was shown to be a species complex of 38 closely related species (Marin-Felix et al 2017), with nine species identified to cause anthracnose in chili (Mongkolporn and Taylor 2018). Morphological characters cannot differentiate many of the species with straight conidia, especially those in the acutatum and gloeosporioides complexes that are pathogens of chili, and multigene phylogenetic analyses are required for proper identification of these species (De Silva et al 2017a)

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