Abstract
Recent taxonomic investigation into genus Pyrrhoderma has determined that the genus currently contains six species, including Pyrrhoderma noxium (formerly Phellinus noxius), and one unnamed, but likely novel species (Zhou et al. 2018). Pyrrhoderma noxium is considered one of the most important pathogens in this genus due to its worldwide distribution in pan-tropical regions, including Asia, Australia, Africa, and Oceania. Pyrrhoderma noxium has a wide host range of over 200 plant species and causes mortality of >100 tropical tree species (e.g., breadfruit, mango) that are integral to economies, native cultures, and forest ecosystems of the Pacific Islands (e.g., Ann et al. 2002). In a previous study, over 100 isolates of P. noxium (as P. noxius) were collected from the Pacific Islands (e.g., Guam, Rota, Saipan, Pohnpei, Yap, Palau, Kosrae, and American Samoa) and other locations (e.g., Japan, Taiwan, Hong Kong, Malaysia, and Australia) and phylogenetic analyses were conducted based on ITS (internal transcribed spacer) and LSU (28S nuclear large sub unit) rDNA gene sequences. Results from this study found that both the ITS and LSU regions provide strong evidence that P. noxium isolates differ from the ex-type culture of P. noxium, suggesting that P. noxium isolates potentially represent one or more undescribed species or distinct genetic groups. Our current work aims to identify the appropriate taxonomic status for the previously characterized distinct genetic groups of P. noxium. Accurate identification of species and/or genetic groups is essential to understanding the true host range and geographic distribution of brown root rot pathogens that are currently comprised within P. noxium. Further, correct identification of the pathogen species or sub-species is critical to develop subsequent measures for detecting and managing the pathogen and its spread, such as creating and enforcing quarantine measures, especially for the widespread and devastating pathogens that are currently considered as P. noxium.
Keywords
Pyrrhoderma,
Pyrrhoderma noxium,
brown root rot
Citation
Garfinkel, Andrea R.; Cannon, Phil G.; Klopfenstein, Ned B.; Stewart, Jane E.; Kim, Mee-Sook. 2020. Identification of genetic groups within the invasive brown root rot pathogen, Pyrrhoderma noxium (formerly phellinus noxius). In: Reynolds, Gregory J.; Wilhelmi, Nicholas P.; Palacios, Patsy, compilers. Proceeding of the 66th Western International Forest Disease Work Conference; 3-7 June 2019; Estes Park, CO. WIFDWC: www.wifdwc.org. p. 141-145.
