Newly discovered basidiocarps of Phellinus noxius on 33 tree species with brown root rot disease in Taiwan and the basidiospore variations in growth rate.

Since 2007, a comprehensive survey of the occurrence of brown root rot disease has been conducted in Taiwan. The rare basidiocarps of the pathogen Phellinus noxius (Corner) Cunningham were also investigated throughout Taiwan and on outer islands. To 2018, a total of 2287 disease cases of brown root rot were recorded, and 164 cases were found with basidiocarps on diseased trees. These 164 cases included 33 newly discovered tree hosts on which were borne the fruiting body of P. noxius. Most of the basidiocarps were of the flat type which is inconspicuous, while some belong to bracket type. Generally, basidiocarps were found in most counties of Taiwan and on the outer islands, but they exhibited higher frequencies in the central and southern parts of Taiwan. They tended to occur more at elevations of 200~300 m in the hills, but gradually disappeared at the elevation increased to 800 m. To compare variations in growth rates, 34 single-basidiospore isolates were obtained and grown on both potato dextrose agar (PDA) and malt extract agar medium (MEA). Results showed three levels of significant growth differences on PDA, and four levels of differences on MEA, indicating growth rate variations among these sexual basidiospores. The abundance of P. noxius basidiocarps in nature suggests that genetically variable basidiospores are involved in long]distance dispersal of this fungus which is responsible for serious tree diseases. [ABSTRACT FROM AUTHOR]