Rust Fungus Pucciniastrum styracinum on Styrax japonicus in Korea Confirmed by Morphological and Molecular Data

Ji-Hyun Park^1,* Bok-Nam Jung^1,2 Jae Sung Lee³ Young-Joon Choi³ Hyeon-Dong Shin⁴

¹Division of Forest Entomology and Pathology, National Institute of Forest Science, Seoul 02455, Korea
²Plant Quarantine Technology Research & Development, Animal and Plant Quarantine Agency,Gimcheon 39660, Korea
³Department of Biology, Kunsan National University, Gunsan 54150, Korea
⁴Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Korea

Abstract

Styrax japonicus is a deciduous shrub or a small tree belonging to the family Styracaceae. Since 1990, a rust fungus has continuously been found on S. japonicus leaves across the country. The morphological characteristics of the rust fungus were most consistent with those of Pucciniastrum styracinum reported on Styrax obassia in Japan. The species identification was confirmed by molecular phylogenetic analysis of the internal transcribed spacer and large subunit rDNA sequences. The current study provides mycological information with morphological measurements and molecular phylogenetic data of P. styracinum found on S. japonicus in Korea. Therefore, this is the first confirmed report on the presence of P. styracinum on S. japonicus in Korea.

Figures & Tables

Fig. 1. occurring on . A, early defoliation of an affected tree in late September, 2020. B, symptoms on the lower leaf surface of affected leaves in the early stage. C, symptoms on the lower leaf surface in the advanced stage. D and E, uredinia formed on the lower leaf surface. F and G. Uredium (F) and urediniospores (G) observed under a scanning electron microscope. H, urediniospores focused on outline under a DIC microscope. I, symptoms on the lower leaf surface with the telial stage. J, vertical section of teliospores on the leaf epidermis on the abaxial side. K, cross section of teliospores seen from the leaf epidermis. abs, abaxial side; ep, epidermis of the leaf; tells, teliospores.