Windflowers (Pulsatilla spp.) are perennial medicinal plants in the family Ranunculaceae with high economic as well as medicinal value in China. It is commonly used as traditional Chinese medicine (1). In May 2012, a root rot disease was observed on windflower (Pulsatilla koreana Nakai) at flowering stages in fields of Liaoning Province, China. The diseased area was estimated to be over 500 ha in the province and the yield was reduced by 30% on average with up to 45% yield losses in some fields. As the disease progressed, brown lesion production extended onto lateral and main roots, and aboveground tissues shriveled and decayed; in severe cases, white mycelium was clearly visible on diseased root tissue. Isolations from symptomatic roots were made on potato dextrose agar (PDA) and single-spore cultures were obtained. Colonies were initially white, but became pale violet with age, and purple pigments were produced in the agar. Microconidia were abundant, unicellular, oval to reniform, and ranged from 5.6 to 13.1 (9.3) × 2.8 to 4.2 (3.2) μm. Macroconidia were sparse, three-septate, slightly curved, and ranged from 21.9 to 39.4 (31.2) × 3.4 to 4.5 (3.9) μm. The isolated fungus was morphologically similar to Fusarium oxysporum (2). Two isolates were selected for molecular identification, and the internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 (3) and sequenced. The obtained sequences (GenBank Accession Nos. JX669525 and JX669526) showed 99% homology with the sequences of F. oxysporum in GenBank (GQ121303). For pathogenicity tests, the isolate was cultured on PDA for 10 days at 25°C. Inoculations were performed on 10 healthy P. koreana plants by spraying a conidial suspension (2.0 × 105 microconidia ml–1) on roots previously wounded with a metal needle. Ten non-treated plants used as controls were sprayed with distilled water. The inoculated plants were incubated at 25°C under conditions of 12/12 h (light and dark). After 2 weeks, root rot symptoms were similar to the original symptoms observed under field conditions. No disease was observed on water-inoculated control plants. The same fungus was reisolated from the roots of infected plants, satisfying Koch's postulates. To our knowledge, this is the first report of F. oxysporum on P. koreana in China. The disease was hitherto scarcely reported in any other countries, and may deserve more attention in the future.
References: (1) S. C. Bang et al. J. Nat. Prod. 68:268, 2005. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Professional, Ames, IA, 2006. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.