The taxonomy of the genus Colletotrichum has undergone tremendous changes over the last decade, with over 200 species being currently recognised and species complexes being informally used to cluster those species. Many of these species are important plant pathogens, some rather polyphagous and others host-specific, but several occur seldomly and some may in fact be ecologically endangered. Based mainly on literature from the past decade, in this work we review the occurrence, geographic distribution and host spectrum of currently recognised Colletotrichum species under phylogenetic, pathological/agronomic and ecological perspectives, providing a list arranged by Colletotrichum species and species complexes. A total of 257 species are listed and grouped into 15 species complexes. In this work we have recorded 1353 unique host species-Colletotrichum species association records from 720 hosts, with the Fabaceae as the family with higher number of hosts (52 host species) but with the Rosaceae as the family with the highest number of host species-Colletotrichum species association records (118 association records). According to occurrence data, 88 species are common in nature, 128 were considered as data deficient and 41 are threatened, some of which are likely extinct from nature and preserved only in culture collections. Several species are relevant plant pathogens, in some cases geographically confined and thus of potential quarantine relevance. Based on the major changes that occurred on Colletotrichum taxonomy over the last decade, this work provides a comprehensive overview of occurrence data of Colletotrichum species, compiling host range and geographical distribution, with relevance for plant pathology and conservation mycology. The current taxonomic framework in Colletotrichum is revealing numerous species but poses challenges to the employment of standard criteria for the evaluation of biological conservation of these fungi. We advocate that conservation mycology and taxonomy should find common routes simultaneously enabling the correct delimitation of species of Colletotrichum and the implementation of feasible criteria for the evaluation of conservation. The employment of new technologies, such whole genome sequencing (WGS), will help and support the description of new species and to gain a better understanding of the genetic bases of speciation processes.

Colletotrichum species and complexes: geographic distribution, host range and conservation status

A leaf spot, found on Sophora tonkinensis in Hechi city, Guangxi province, China was identified as Colletotrichum siamense based on morphological and molecular phylogenetic analysis of the internal transcribed spacer (ITS) of ribosomal DNA, β-tublin (TUB2), the translation elongation factor 1-alpha (TEF1-α), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), chitin synthase 1 (CHS-1), calmodulin (CAL) and glutamine synthetase (GS) genes. Koch’s postulates were satisfied by successful reisolation of C. siamense only from plants inoculated with the pathogen. This is the first report of leaf spot caused by C. siamense on Sophora tonkinensis.

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First report of leaf spot caused by Colletotrichum siamense on Sophora tonkinensis

【Objective】To provide scientific basis for extention of a South China origin woody grain potential plant, Steculia nobilis Smith (SNS), its seed embryo, the edible part of the plant was investigated on the characteristics of nutrition and health care. 【Method】A comprehensive research was performed to determine nutritional compositions and antioxidant activities of polyphenols in seed embryo of two kinds of SNS (GXPN01 and GXDX01 ). 【Result】The results indicated that the nutrient compositions of SNS seed embryo mainly consisted of starch and protein , and exhibited rich fat , starch , vitamin , polyphenol , amino acid and trace elements (Ca , Fe , Zn ) , and vitamin C and vitamin E contents were considerably higher than other vitamins. Additionally, SNS seed embryo contained considerable polyphenols (especially flavonoids ), which possessed stronger antioxidant potential by evaluating reducing power , metal chelating capacity and radical-scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH), and hydroxyl radical- and superoxide anion-scavenging activity. 【Conclusion】Sterculia nobilis Smith is strongly recommended woody food plant for its nutritional seed embryo with health care results including antioxidant activities.

Nutritional and health care valuation of seed embryo Sterculia nobilis Smith

Sterculia lanceolata, an important tropical woody plant, has high ornamental and medicinal value. To our knowledge, only brown root disease in this plant has been reported. In Nanning, Guangxi, China, an outbreak of leaf blight disease was observed on S. lanceolata in June 2019, with the leaf infection rate ranging from 80% to 100%. The disease seriously affected the leaves of trees and caused economic loss. Eight isolates were recovered from the infected leaves of different trees, and the pathogenicity was then determined by the methods of mycelial disc and conidial suspension, fulfilling Koch's postulates. According to the morphological and molecular biological characteristics of isolates, the pathogen causing leaf blight on S. lanceolata was identified as Colletotrichum siamense. Accurate identification of the pathogen provides a reliable basis for the control of the disease.

Morphological and molecular identification of Colletotrichum siamense, a novel leaf pathogen associated with Sterculia lanceolata recorded in China

Abstract The EFSA Plant Health Panel performed a pest categorisation of Colletotrichum aenigma, C. alienum, C. perseae, C. siamense and C. theobromicola, five clearly defined fungi of the C. gloeosporioides complex causing anthracnose. The pathogens are widely distributed in at least three continents. C. aenigma and C. siamense are reported from Italy and C. alienum from Portugal, including the Madeira Islands, with a restricted distribution. C. perseae and C. theobromicola are not known to be present in the EU. However, there is uncertainty on the status of the pathogens worldwide and in the EU because of the taxonomic re‐evaluation of the genus Colletotrichum and the lack of specific surveys. The pathogens are not included in Commission Implementing Regulation (EU) 2019/2072 and there are no reports of interceptions in the EU. With the exception of C. perseae, which has a very limited number of hosts, the other four Colletotrichum species have relatively wide host ranges. Therefore, this pest categorisation focused on those hosts for which there is robust evidence that the pathogens were formally identified by a combination of morphology, pathogenicity and multilocus sequence analysis. Host plants for planting and fresh fruits are the main entry pathways into the EU. Host availability and climate suitability factors occurring in some parts of the EU are favourable for the establishment of the pathogens. No yield losses have been reported so far in the EU but in non‐EU areas of their current distribution, the pathogens have a direct impact on cultivated hosts that are also relevant for the EU. Phytosanitary measures are available to prevent the further introduction and spread of C. aenigma, C. alienum and C. siamense into the EU as well as the introduction and spread of C. perseae and C. theobromicola. C. aenigma, C. alienum, C. perseae, C. siamense and C. theobromicola satisfy the criteria that are within the remit of EFSA to assess for these species to be regarded as potential Union quarantine pests.

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Pest categorisation of Colletotrichum aenigma , C. alienum , C. perseae , C. siamense and C. theobromicola

Sterculia nobilis is an important tropical woody plant with high ornamental and economic value. At present, there are few reports of diseases on this plant. In August 2018, an unknown leaf spot disease was observed on S. nobilis in Nanning, China, affecting the inner leaves of the canopy and causing considerable defoliation. The pathogen was isolated, and pathogenicity tests carried out on detached leaves to verify Koch's postulates. Based on morphological observations and polygenic analyses, the pathogen causing leaf spots on S. nobilis was identified as Colletotrichum siamense.

Rong Shen

Papers

Colletotrichum siamense: A novel leaf pathogen of Sterculia nobilis Smith detected in China