Taxonomy and pathogenicity of two novel Chrysoporthe species from Eucalyptus grandis and Syzygium guineense in Zambia

Among fungi in the Cryphonectriaceae, Cryphonectria parasitica, the causal agent of chestnut blight, and Chrysoporthe spp., inducing stem cankers and death of plantation-grown Eucalyptus spp., constitute some of the most important tree pathogens. During a survey to determine diseases and related pathogens associated with native and non-native Myrtales in Zambia, two fungi resembling stem canker pathogens in the genus Chrysoporthe were recovered from Syzygium guineense and Eucalyptus grandis. We undertook this study to characterise the fungi, using DNA sequence comparisons and morphological features. Inoculation tests were also conducted in a greenhouse to assess their pathogenicity on Eucalyptus spp. Results showed distinct phenotypic differences between isolates collected from Zambia and existing species of Chrysoporthe, and phylogenetic analyses demonstrated that the Zambian isolates represent previously undescribed species of Chrysoporthe. These isolates, which have been named Chrysoporthe zambiensis sp. nov. and Chrysoporthe syzygiicola sp. nov., are only known from their anamorphic states. Both species were found to be pathogenic to Eucalyptus. The description of Chr. zambiensis and Chr. syzygiicola with teleomorph names, led to the new combination Chrysoporthe hodgesiana for the only anamorphic species in Chrysoporthe, Chrysoporthella hodgesiana, to ensure more stable and less confusing taxonomy for Chrysoporthe.