Exobasidium Fungi (Ustilaginomycotina, Basidiomycota) Isolated from Asymptomatic Leaves of Abies firma

Exobasidium Fungi (Ustilaginomycotina, Basidiomycota) Isolated from Aasymptomatic 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

*Email: s2320975@u.tsukuba.ac.jp

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. Their behavior outside symptomatic periods, primarily in spring and early summer, remains unclear. Despite host specificity as the pathogen, the previous finding suggested 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 the Exobasidium fungal isolates were specified  by BLAST searches. The phylogenetic analysis of those isolates was conducted based on the sequences of rDNA ITS and LSU regions. Of 104 isolates, 28 Exobasidium fungi were divided into six clades, including at least four known species by the phylogenetic analysis, and suggested to live and firmly adhere to A. firma leaves without causing symptoms. These findings indicate that Exobasidium species inhabit beyond those previously reported as hosts.