Isolation and Identification of an Unreported Fungal Species in Korea and Novel Ice Nucleation Active Fungus: Fusarium diversisporum

Diane Avalos-Ruiz Gwang-Jae Lim¹ Seong-Keun Lim¹ Leonid N. Ten¹ In-Kyu Kang¹ Seung-Yeol Lee^1,3,* Hee-Young Jung^1,3

¹School of Applied Biosciences, Kyungpook National University, Daegu 41566, Korea
²Department of Horticultural Science, Kyungpook National University, Daegu 41566, Korea
³Institute of Plant Medicine, Kyungpook National University, Daegu 41566, Korea

Abstract

In this study, the fungal strain KNUF-21-F39 was isolated from a declined apple tree (Malus domestica) in the Chungcheongbuk province in Korea. The strain KNUF-21-F39 presented a slow growth rate and a variety of macroconidia shapes and sizes ranging from ovoid to fusoid and 1- to 5-septate, primarily showing 3- and 4-septate, with “S” -shaped macroconidia rarely observed. The strain was identified based on morphological characteristics along with phylogenetic analysis performed using the internal transcribed spacer region (ITS) and partial sequences of translation elongation factor 1-α (tef1), RNA polymerase largest subunit (rpb1), and calmodulin (cal) genes. The fungal strain KNUF-21-F39 was identified as Fusarium diversisporum, which has not been previously reported in Korea. The ice nucleation activity (INA) of the strain was also evaluated, identifying the strain as positive for INA. This is the first report characterizing F. diversisporum as an IN-active fungal species.

Figures & Tables

Fig. 1. Morphological characteristics and ice nucleation activity of KNUF-21-F39. A, Colony formation on potato dextrose agar (PDA) after ten days. B, Colony formation on oatmeal agar after ten days. C, Macroconidia observed after 60 days of growth in PDA. D, Ice nucleation activity of the strain observed using the tube-freezing essay. E, Ice nucleation negative control (without freezing). Scale bars: 10 μm.