Morphological and molecular identification of Colletotrichum species associated with cassava anthracnose in Thailand

Abstract

The objective of this study was to identify the causal agent of anthracnose disease of cassava in Thailand. The study was carried out by collecting cassava samples with anthracnose symptoms from various planting areas including 10 districts of eight provinces in Thailand. One hundred and thirty‐six Colletotrichum samples were isolated from cassava anthracnose lesions on leaves, petioles and stems. Thirty‐eight single‐spore isolates were subsequently obtained and cultured on half potato dextrose agar for morphological and molecular characterizations. All 38 isolates were pathogenic with varying degrees of virulence when tested on detached leaves of Kasetsart 50, a susceptible cassava cultivar. Based on their growth habit, colony morphology, conidial morphology and the internal transcribed spacer sequences similarity to that of Colletotrichum accessions in the GenBank, one isolate was identified as C. capsici, one as C. lindemuthianum, two as C. aeschynomene, four as C. boninense and 28 C. gloeosporioides species complex. Geographically, the cosmopolitan C. gloeosporioides species complex was found in all regions, but other species were found only in particular regions. This is, so far, the first report of Colletotrichum complex species associated with cassava anthracnose in Thailand.

Colletotrichum species associated with cassava anthracnose in China

“…Colletotrichum gloeosporioides f.sp. manihotis had previously been shown to be the causal agent of CAD in cassava (Amusa, ; Kunkeaw et al, ; William, Mbega, & Mabagala, ); however, five Colletotrichum species have recently been identified as a complex, using morphological and ITS molecular characterizations in Thailand (Sangpueak et al, ). We confirmed that identification to species level in the Colletotrichum complex requires multiple‐loci phylogeny, where we combined six gene (GAPDH, ITS, CAL, ACT, TUB2 and GS) in an analysis, that found that the combination of four gene (ACT, TUB2, GAPDH and ITS) was sufficient to separate species from the C. boninense and C. orchidearum species complexes.…”

“…Increasing demands for cassava have resulted in the expansion of the cultivation area, and changes in crop management practice that have led to an increase in diversity and incidence of injurious disease. Cassava anthracnose disease (CAD) is one of the most important diseases of cassava, especially in Africa and in Thailand (Hahn, Isoba, & Ikotun, ; Sangpueak, Phansak, & Buensanteai, ), where affected plants are characterized by necrotic lesions on the leaf, stem and base of the leaf petiole (Li et al, ) that lead to leaf wilt, shoot‐tip die back and defoliation (Owolade, ). CAD is a common, but minor disease of cassava in Guangxi, Hainan and Yunnan, however its incidence and effects increase during the wet season in parts of Yunnan and Guangxi.…”

“…The fungal pathogen Colletotrichum gloeosporioides f.sp. manihotis has been identified as the most common causal agents of CAD (Amusa, ; Kunkeaw, Worapong, Smith, & Triwitayakorn, ), where identification of the pathogen has previously relied on morphological characteristics that may not allow differentiation of similar species (Sangpueak et al, ). Indeed, it has been (Sutton, Bailey, & Jeger, ) suggested that species identification within the genus Colletotrichum is unlikely to based solely on morphology, and evidence of morphological plasticity and phenotypes overlap within this genus (Cai et al, ; Liu, Wang, & Damm, ) indicates that alternative approaches to ensure accurate identification of the congeneric species are required.…”

“…boninense and C . gloeosporioides species complexes (Sangpueak et al, ), while C. gloeosporioides and C. graminicola were identified causal agents of CAD in China (Cai, Li, Shi, Lin, & Huang, ; Lu, ). However, it is not possible to rely sequences of ITS regions in isolation to resolve taxonomic problems in species complexes; therefore, a polyphasic approach that combines the application of multi‐locus phylogenetic analysis with morphological data has been applied to Colletotrichum and has revealed many cryptic and new species in many cases (Cannon et al, ; Damm et al, ,; Damm, Cannon, Woudenberg, & Crous, ; Damm, Cannon, Woudenberg, Johnston, et al, ; Marin‐Felix et al, ; Weir et al, ).…”

Using Agrowastes in Mushroom Production and Compost Recycling to Control Cucumber Anthracnose Caused by Colletotrichum orbiculare

“…Many workers in the field of taxonomy concluded that morphological characters alone were not reliable criteria for Colletotrichum identification and have failed to resolve the phylogenetic relationships among the species (Weir et al, 2012;Chen et al, 2015 andSangpueak et al, 2017). Khalil, et al (2018) stated that advanced technologies such as polymerase chain reaction (PCR) besides morphological characters in identifying members of the genus Colletotrichum has become necessary.…”