First Report of Phytophthora Blight of Lily Caused by Phytophthora nicotianae in China.

Lily (Lilium spp.) is an economically important cut flower in China. In August 2009, 30 to 40% of plants of lily cv. Siberia in a greenhouse for cut flower production in Yunnan, China were severely diseased. Infected plants developed water-soaked lesions and soft rot on the base of stems and leaves near the soil surface. As the disease progressed, stems bent and plants collapsed. Soft rot symptoms were observed on some bulbs and roots of severely diseased plants. Small, diseased tissue fragments (approximately 3 mm) were surface disinfected with 0.5% NaOCl and then plated to Phytophthora selective medium (10% V8 juice agar) (4). Inoculated dishes were incubated at 25°C in the dark. After 5 days, white colonies with abundant aerial mycelia developed from all plated tissue samples. The fungus had aseptate hyphae. Sporangia were papillate, both caducous and noncaducous, and the shape ranged from ovoid to spherical. The dimensions of sporangia were 30 to 62 × 21 to 46 μm. On the basis of morphological features, isolates were identified as Phytophthora nicotianae Breda de Haan. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS1/ITS4 and sequenced. BLAST analysis of the 835-bp fragment showed a 99% homology with the sequence of P. nicotianae AY833527. The nucleotide sequence has been assigned GenBank No. GU299778. PCR amplification of genomic DNAs using the P. nicotianae-specific primer pair ITS3-PNIC1 generated a 455-bp sequence (3). The result further confirmed the identity of P. nicotianae. Pathogenicity tests were conducted in the greenhouse on lily cv. Siberia grown in pots. Ten 3-month-old plantlets were inoculated by watering the wounded stem bases and soil surface with 30 ml of zoospore suspensions (10 spores per ml). Five uninoculated plantlets were used as controls. All plantlets were covered with plastic bags and incubated at room temperature (22 to 26°C) for 48 h. Inoculated plants developed initial symptoms of slight chlorosis and wilting of lower leaves. Within a 3-week period, all plants died due to soft rot of stem bases and leaves. The pathogen was reisolated from inoculated plants but not from control plants that were symptomless. P. nicotianae has been reported as the causal agent of Phytophthora blight on lily in Korea, Japan, and Hungary (1,2). To our knowledge, this is the first report of Phytophthora blight of lily in China. References: (1) J. Bakonyi et al. Plant Pathol. 50:795, 2001. (2) H. J. Jee and W. G. Kim. Plant Pathol. J. 14:452, 1998. (3) P. W. Tooley et al. Appl. Environ. Microbiol. 63:1467, 1997. (4) X. B. Zheng. Phytophthora and Its Research Technology. Beijing. China Agriculture Press, Beijing, 1997.