Occurrence in Korea of Rust Disease on Tilia mandshurica Caused by Pucciniastrum tiliae

Tilia mandshurica trees with rust symptoms have consistently been noticed during disease surveys in Korea since 2006. Based on the morphological examination and molecular sequence analysis of the internal transcribed spacer and large subunit of ribosomal DNA, Pucciniastrum tiliae was identified as the causal fungus of rust disease. This is the first report of P. tiliae infection on T. mandshurica in Korea.

Tilia spp. (Malvaceae) are widely distributed throughout the temperate northern hemisphere including Asia, Europe, and eastern North America [1]. T. mandshurica Rupr. & Maxim., commonly named ‘mandshurian linden’, is a deciduous tree and native to northeastern Asia including China, Japan, Korea, and Russia (Siberia). In Korea, the tree is one of the most common trees in gardens and parks and a nectar source of small pollinators such as honeybees and flies [2]. On T. mandshurica, a rust fungus (Pucciniastrum tiliae) has been recorded from Japan and China, along with a dieback and canker-causing fungus (Nectria dematiosa from China) and two powdery mildew fungi (Erysiphe clintonii from USA and E. oleosa var. zhengii from Russia) [3]. Pucciniastrum tiliae is known to form spermogonial and aecial stages onAbies spp. but uredinial and telial stages onTilia spp. [4]. After a rust disease was observed on T. mandshurica, planted in an experimental forest of Korea University (37°30'20"N; 127°41'56"E), Yangpyeong, Korea in August 2006, it has been consistently observed in Goseong, Hoengseong, and Incheon. The rust disease on T. mandshurica caused premature defoliation (Fig. 1A). The affected leaves were discoloured and became yellow. Uredinia were formed on the lower leaf surfaces (Figs. 1B and C). The present study aimed to record this new rust disease on T. mandshurica in Korea and to identify the causal fungus based on morphological characteristics and molecular sequence data.