Puccinia kusanoi Dietel is a known causal agent of rust on some species of bamboo (subfamily Bambusoideae, Poaceae) (Hiratsuka et al. 1992). Deutzia spp. are the aecial hosts of P. kusanoi (Asuyama 1936; Hiratsuka et al. 1992). The rust fungus has been reported on Deutzia pulchra Vidal in Taiwan (Hiratsuka and Chen 1991; Shen et al. 2016). To determine the prospective telial and uredial host, an investigation was carried out on Yushan cane (Yushania niitakayamensis (Hayata) Keng f.), the only bamboo species naturally grown close to D. pulchra at Tataka, Nantou, Taiwan, at an elevation of 2,600 m. In May 2016, rust disease was discovered on leaves of Yushan cane at Tataka, with more than 20% of plants in the region showed rust symptoms. Brownish lesions surrounded with yellow halos were seen on the leaves. Uredinia were brown, erupting through the epidermis on the abaxial side of leaves. Uredinospores were orange to brown, echinate, obovoid, broadly ellipsoid, with an average length and width of 30.9 (26.3 to 35.0) × 25.1 (22.5 to 28.1) μm (n = 40), walls 1.3 to 2.5 μm thick. Telia were brown, convex on abaxial leaf surfaces. Teliospores were orange, smooth, 2-celled, oval to obtuse cylindrical, spore shapes tending dimorphic, slightly constricted or not constricted at septum, with an average length and width of 65.1 (45.0 to 79.4) × 21.8 (18.1 to 26.3) μm (n = 40), walls 1.0 to 2.5 at sides, 3.2 to 8.8 apically. Since the morphology of the specimens fits in with the descriptions of P. kusanoi collected in Japan (Cummins 1971; Hiratsuka et al. 1992), the rust fungus on Yushan cane was identified as P. kusanoi. Two voucher specimens, TNM nos. F0029955 and F0029956, were deposited in the herbarium of the National Museum of Natural Science, Taichung, Taiwan. Amplifications of the 28S large-subunit (LSU) rDNA, internal transcribed spacer (ITS) region, and 18S small-subunit (SSU) rDNA were carried out as in Shen et al. (2016). A contig sequence covering the SSU, ITS, and LSU rDNA region of TNM F0029955 specimen was obtained and deposited in GenBank (accession no. KX610657). The sequence is 99.9% identical to those of Aecidium deutziae (KU309316 to 18) on D. pulchra collected at the same locality (Shen et al. 2016) over a 3,380-bp alignment. The result suggests that P. kusanoi alternates between Y. niitakayamensis and D. pulchra to complete its life cycle in mountainous areas in Taiwan. To our knowledge, this is the first report of P. kusanoi infecting Yushan cane. Remarkably, this is the first record of rust disease on the bamboo genus Yushania. © The American Phytopathological Society.
