Severe Outbreak of Rust Caused by Coleosporium pulsatillae Detected on Pulsatilla spp. in China.

ABSTRACT

Windflower (Pulsatilla spp.) is a perennial medicinal plant in the Ranunculaceae with high economic value as well as medicinal value in China. It is a commonly used Chinese herbal medicine. In 2007, two species, Pulsatilla koreana Nakai and P. chinensis Regel, were observed with severe rust symptoms at three locations (Shenyang City, Benxi City, and Fushun County) in Liaoning, China. The diseased area was estimated to be more than 500 ha and the yield was reduced by 30% on average with up to 65% yield losses in some fields. Since its first record in 2007, the disease has been recorded every year in parts of China. A survey of all cultivated fields in August 2011 revealed that 90% of the Pulsatilla plants were heavily infected with rust. Early symptoms on the adaxial leaf surfaces were small, circular, yellow spots that later enlarged, coalesced, and developed necrotic centers. On the abaxial side, numerous yellow rust uredinia were visible. Urediniospores are globose or ellipsoidal, sometimes angular in shape, with a yellowish content, and measured 22.6 to 39.4 × 15.2 to 23.9 µm. Spore walls were coarsely verrucose when examined by light and scanning electron microscopy. Telia and teliospores were observed in mid-August. Hypophyllous telia often formed around uredinial clusters. Telia were 0.3 to 1.1 mm wide and erumpent with numerous teliospores in a compact layer. Teliospores were clavate, oblong to ellipsoidal, 60.2 to 120.8 × 12.1 to 24.4 µm, gelatinous, and one celled. Teliospores were four celled with the division of the protoplast into an internal four-celled basidium. Pathogenicity tests included inoculation of young P. koreana plants by spraying a urediniospore suspension (30,000 spores/ml of deionized water). Inoculated plants were incubated at 25°C for 48 h, and typical rust symptoms and uredinia developed in 10 to 15 days. On the basis of symptomatology, the host, and morphology of uredinial and telia, the fungus was identified as Coleosporium pulsatillae (Str.) Lév (2). The internal transcribed spacer (ITS) region was amplified using ITS1-F and ITS4-B primers (3), and an amplified product of 817 bp, specific for the species C. pulsatillae, was obtained. The sequence was deposited in GenBank (Accession No. JQ029765). Although this pathogen has been mentioned as part of a fungal species survey from China, it was not fully described (4). This pathogen has been reported on Anemone chinensis in Austria, Sibiria (2), and Korea (1). It has not been reported from anywhere else in China. To our knowledge, this is the first fully described record and most severe outbreak of C. pulsatillae on windflower. References (1) W. D. Cho and H. D. Shin. List of Plant Diseases in Korea. Korean Society of Plant Pathology, Seoul, Korea, 2004. (2) J. B. De-Toni. Sylloge Fungorum 7754, 1888. (3) M. Gardes et al. Mol. Ecol. 2113, 1993. (4) F. L. Tai. Sylloge Fungorum Sinicorum. Science Press, Beijing, 1979.