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Litchi (Litchi chinensis) is an evergreen fruit tree grown in subtropical and tropical countries. China accounts for 71.5% of the total litchi cultivated area in the world. Anthracnose disease caused by Colletotrichum species is one of the most important diseases of litchi in China. In this study, the causal pathogens of litchi anthracnose in Hainan, China, were determined using phylogenetic and morphological analyses. The results identified eight Colletotrichum species from four species complexes, including a proposed new species. These were C. karsti from the C. boninense species complex; C. gigasporum and the proposed new species C. danzhouense from the C. gigasporum species complex; C. arecicola, C. fructicola species complex; C. arecicola, C. fructicola and C. siamense from the C. gloeosporioides species complex; and C. musicola and C. plurivorum from the C. orchidearum species complex. Pathogenicity tests showed that all eight species could infect litchi leaves using a wound inoculation method, although the pathogenicity was different in different species. To the best of our knowledge, the present study is the first report that identifies C. arecicola, C. danzhouense, C. gigasporum and C. musicola as etiological agents of litchi anthracnose. [ABSTRACT FROM AUTHOR]

Areca palm, rubber tree, and coffee are always planted adjacent to each other or intercropped with each other, and Colletotrichum siamense was found to be the dominant species of Colletotrichum from these crops in Hainan, China. To study the population structure, pathogenicity, and fungicide sensitivity of C. siamense from these three crops in Hainan, isolates were first identified by their morphological characteristics and multilocus phylogeny. Then both permutational multivariate analysis of variance (PERMANOVA) and pairwise FST analysis showed that the original host and geographical origin (counties) had significant effects on genetic variation in the C. siamense population, explaining 5.6% and 16.3% of genetic variation, respectively. There were significant genetic differentiations between coffee and rubber tree populations but the genetic differentiation was small (FST = 0.04), while significant differentiations were observed among all populations from different counties except those between Haikou and Chengmai. Pathogenicity analysis using artificial inoculation showed that isolates had significantly higher disease incidence and diseased lesion diameter on wounded leaves than on nonwounded leaves. However, the original host of an isolate and geographical origin did not significantly affect the pathogenicity of the C. siamense populations from these three hosts. In vitro tests showed that there were no significant differences in the sensitivity of C. siamense populations to carbendazim, prochloraz, difenoconazole, and propiconazole from different original hosts and geographical origins. The present study suggests that host specialization of C. siamense has not occurred yet in coffee, rubber tree, and areca palm. [ABSTRACT FROM AUTHOR]