Aurantioporthe corni gen. et comb. nov., an endophyte and pathogen of Cornus alternifolia

Abstract

Cryptodiaporthe corni is the causal agent of a destructive disease called golden canker, which affects Cornus alternifolia, known as the pagoda or alternate-leaved dogwood. Due to the association between Cr. corni and pagoda dogwood, we sought to determine whether this fungus was capable of living as an endophyte in pagoda dogwood and causing this disease. Forty asymptomatic stems of plants growing in nature were sampled from five sites across Minnesota. Cryptodiaporthe corni was present in more than half (62.5%) of the stems. Asymptomatic nursery material also was sampled, and the fungus was isolated from a small percentage (20%) of them. Inoculations carried out in the field and greenhouse suggested the endophytic isolates of Cr. corni were capable of causing disease. Asymptomatic stems of trees in the field inoculated with non-colonized (control) grain seed developed golden canker as frequently as those inoculated with grain seed colonized by Cr. corni, suggesting that the fungus was already present in these plants. In greenhouse pathogenicity trials an isolate of Cr. corni obtained from an asymptomatic stem was capable of causing golden canker disease, thus demonstrating causality, fulfilling Koch’s postulates. The taxonomic placement of Cr. corni within Cryphonectriaceae was determined. Phylogenetic analysis of the ITS rDNA and β-tubulin gene regions, along with morphological characteristics, suggested Cr. corni is distinct from other genera within this family. Therefore, we propose a new genus, Aurantioporthe, as well as the new combination, A. corni, to accommodate this species within Cryphonectriaceae.

• Cryphonectriaceae
• Diaporthales
• golden canker
• pagoda dogwood

Acknowledgments

We thank Dr Fredrick Barker and Dr Benjamin Held for their assistance with the phylogenetic analysis. Also we thank Ellen Bloch and Dr Barbara Thiers (New York Botanical Garden), Dr Amy Rossman (USDA-ARS) and Anita Cholewa (Bell Museum of Natural History) for their assistance in acquiring herbarium specimens. We also are thankful for Dr Rossman’s assistance with reviewing the manuscript and helpful comments. We thank Kathleen Kitka, Amy Highland, Robert Mulrooney, Sarah Rummery, Andy Schmitz, William Cullina, Linda Blue and Tracy Beerley for sending samples of stems infected with Aurantioporthe corni. This work was supported by the USDA National Institute of Food and Agriculture, Hatch Project MIN-22-055 and MIN-21-055.