Exobasidium Fungi (Ustilaginomycotina, Basidiomycota) Isolated From Asymptomatic Leaves Of Abies Firma
Satomi Akinari*¹ and Izumi Okane²
¹Agro-Bioresources Science and Technology, Univ. of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
²Institute of Life and Environmental Sciences, Univ. of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
The diversity of Basidiomycota inhabiting the phyllosphere has often been underestimated through ordinary culturing methods, particularly slow-growing basidiomycetes. We have sought to reveal the diversity of phyllosphere basidiomycetes, especially those firmly adhering to plants. Our previous DNA detection identified Exobasidium spp. in evergreen trees, including non-Ericales, although diseases caused by them have only been reported in Ericales. The behavior of these fungi outside symptomatic periods, primarily in spring and early summer, remains unclear. Despite host specificity as the pathogen, the previous finding suggests that they may inhabit non-host plants. Indeed, they have been isolated from non-host plants by leaf wash plating, but the topic remains under study. This study aimed to explore the diversity of Exobasidium fungi within Abies firma, not previously reported as the host. Asymptomatic A. firma leaves were treated ultrasonically with a 0.005% Aerosol® OT, a surface-active agent. The crushed-leaf solution was plated on either PDA or selective media and incubated for over three weeks at 25℃. Basidiomycetes were selected from the isolates through PCR amplification, using a basidiomycete-specific primer set, and BLAST searches were conducted to specify the Exobasidium fungal isolates. The phylogenetic analysis of those isolates was conducted based on the sequences of rDNA ITS and LSU regions. Of 104 isolates, 18 Exobasidium fungi were suggested to be assigned to five species by the phylogenetic analysis, and they live and firmly adhere to A. firma leaves without causing symptoms. These findings strongly indicate that Exobasidium species inhabit beyond those previously reported as hosts.