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Common identification systems in Colletotrichum include traditional morphological taxonomy, molecular classification, secondary metabolites and some other traits. All these identification systems alone may cannot unequivocally place an isolate in Colletotrichum species complex. It is important to incorporate morphological identification, multi-gene phylogenetic analysis and secondary metabolites analysis to identify Colletotrichum (Cai et al. 2009), therefore, enhancing the accuracy of Colletotrichum species identification.
Based on morphology and the five-gene-combined phylogenetic analysis, 136 Colletotrichum isolates on mango from southern China were identified as 14 species including C. asianum, C. siamense, C. fructicola, C. gloeosporioides, C. karstii, C. musae, C. endophytica, C. scovillei, C. cordylinicola, C. tropicale, C. gigasporum, C. cliviae, C. liaoningense and C. jiangxiense. Four species complex: C. gloeosporioides, C. acutatum, C. gigasporum C. boninense (Weir et al. 2012, Damm et al. 2012a, 2012b; Liu et al. 2014). The morphological descriptions of the isolates were consistent with the description of Colletotrichum, but the cultural characteristics may be diverse due to varied cultural conditions, and the conidial morphology could not distinguish the targeted species within the species complex (Weir et al. 2012).
Currently, eleven Colletotrichum species on mango have been reported worldwide and these species are C. asianum, C. fructicola, C. siamense, C. tropicale, C. dianesei, C. karstii, C. cliviae, C. endomangiferae, C. kahawae, C. theobromicola (syn. C. fragariae), C. grossum (Lima et al. 2013; Vieira et al. 2014; Sharma et al. 2013; Rojas et al. 2018; Pardo et al. 2016; Leon et al. 2018). Mo et al. (2018) identified three Colletotrichum species (C. asianum, C. siamense, C. fructicola) on mango in Guangxi province in China. In this study, however, except for C. asianum, C. siamense, C. fructicola, there were 11 Colletotrichum species (karstii, C. endophytica, C. scovillei, C. cliviae, C. gigasporum, C. gloeosporioides, C. jiangxiense, C. liaoningense, C. musae, C. tropicale, C. cordylinicola) were the first report on mango in China. This research is also the first report for C. gigasporum, C. cordylinicola, C. musae, C. jiangxiense, C. liaoningense and C. endophytica associate with mango anthracnose in the world. In addition, this study also generated seven isolations that not aligned with any existing species analysed. Further analysis are in need for these isolations.
Colletotrichum asianum, C. siamense and C. fructicola were found to be the dominant species associate with mango anthracnose in China (Mo et al. 2018). This finding is in agreement with what was reported by Vieira et al. (2014 ) who found that C. asianum was the most common endophytic species from mango trees. Colletotrichum asianum and C. siamense, were report as pathogens in a wide range of hosts such as Coffea arabica, Carica papaya and M. indica (Pardo-De la Hoz et al. 2016; Lima et al. 2015; Weir et al. 2012). Our study showed that one host species may be infected by several Colletotrichum species, and this was previously reported by Phoulivong et a. (2012). Colletotrichum fructicola was initially reported on coffee berries, and it also has a wide host range (Arachis sp., Citrus bergamia, M. indica) as well as wide geographical distribution (Viera et al. 2014). Similarly, C. tropicale were reported on Annona muricata (Annonaceae), Viola surinamensis (Myristicaceae) and M. indica in Brazil (Jayawardena et al., 2016).
Colletotrichum musae was a major causal agent of banana anthracnose and associated with fruit disease spots for Musa sp. in many countries (Jayawardena et al. 2016). Colletotrichum cliviae were found to be associated with anthracnose of Clivia miniata, Cymbidium hookerianum in China (Yang et al. 2009, 2011, Wang et al. 2016) and on Phaseolus sp. and Saccharum sp. in India (Chowdappa et al. 2014). It was also reported as an endophyte on M. indica in Brazil (Vieira et al. 2014).
Colletotrichum gloeosporioides was a main pathogen from Citrus sp., Mangifera sp., Vitis vinifera and so son., and it had a wide host range in lots of publications because many Colletotrichum were identified as C. gloeosporioides (Jayawardena et al. 2016) previously. In the present study, C. asianum, C. siamense, C. fructicola, C. tropicale, C. gloeosporioides, C. musae, C. kahawae and C. cordylinicola belongs to the C. gloeosporioides species complex (Weir et al. 2012), and these results were consistent with previous reports that C. gloeosporioides were the main causal agent of mango anthracnose (Arauz et al. 2000).
Colletotrichm scovillei were reported as pathogens on Capsicum sp. (chilli “Django”) by Cueva et al. (2018), and belongs to the C. acutatum species complex (Damm et al. 2012). Colleotrichum karstii was first reported from orchids and was also known from some other hosts such as Carica papaya, Citrus sp., and M. indica (Damm et al. 2012, Wang et al. 2016). Colletotrichum karstii were found on mango and avocado fruit (Lima et al., 2013, Giblin et al. 2018), and it belongs to the C. boninense species complex (Damm et al. 2012).
Colletotrichum gigasporum belongs to the C. gigasporum species complex. The species has large conidia and its wide range hosts were Acacia auriculiformis and Coffea sp. (in Vietnam), Diospyros kaki and Musa sp. (in Japan). Colletotrichum endophytica were found on Pennisetum purpureum in Thailand and tea plant in China (Wang et al., 2016). Colletotrichum jiangxiense was reported as a pathogen and also an endophyte from Camellia sinensis in China (Liu et al. 2015). Colletotrichum liaoningense was first report as a pathogen of Capsicum annuum var. conoides in China (Fu et al. 2019).
The present study revealed high species diversity among collected mango Colletotrichum species from the six major mango-grown areas in China: Yunnan, Hainan, Guizhou, Sichuan, Guangdong and Fujian provinces. The Colletotrichum isolates of mango from different area of China examined in this study showed diversity, which may correlates with environmental conditions such as temperature and rainfall (Veloso et al. 2018) and the sample collecting time and isolation source of Colletotrichum spp.
Pathogenicity test using fourteen species of Colletotrichum isolates showed that all species were pathogenic to mango leaves and fruits in the wound-inoculation experiment. The pathogenicity test results showed that the virulence of Colletotrichum isolates to fruit and leaves was not completely consistent, but the virulence of different isolates was found to be significantly different. The difference in virulence of Colletotrichum within species was independent of a particular geographical origin for sample collection and may vary with the infections and environmental conditions of the isolates. There were more isolates having weak virulence in Yunnan province and considered to be highly virulent in Hainan province. Symptoms may vary considerably with factors such as the mango cultivar, conditions of the fruit, humidity and temperature, and the inoculum concentration (Freeman et al. 1998). Thus, the pathogenicity test results from this study may not reflect the full virulence potential. Additional research should be conducted to determine the virulence for Colletotrichum species in vivo rather than just on detached leaves and fruits.
This study enhanced our understanding on the diversity of Colletotrichum species associate with mango anthracnose in China. Further study is required to determine whether or not there is a difference in biological and infection characteristics between various mango Colletotrichum species as well as on how the molecular mechanisms responsible for the virulence differentiation and spread in anthracnose disease. In addition, there have been few studies on the pathogenesis of Colletotrichum species on mango. Therefore, future work on pathogenic mechanism could be helpful with a reference for the prevention and control of anthracnose disease.

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