Proof for the Occurrence of Flower Blight Caused by Ciborinia camelliae in Italy

Abstract

Camellia cultivation has a long history in the Lake Maggiore area of Northern Italy where a wide selection of varieties is present. In March to April 2001, a previously unconfirmed flower blight was observed on a collection of camellia varieties grown in a garden. Initial symptoms included the appearance of irregular, small, brown spots on the petals. Under favorable temperature and moisture conditions, the lesions enlarged rapidly and coalesced to form large spots that turned the entire petal brown. When the infection reached the base of the petal, it spread to other petals of the flower and finally caused the entire flower to show symptoms of blight. Eventually, the whole flower became uniformly dull brown and dropped from the plant. At the bases of infected flowers, a white or gray ring of mycelium was seen when the calyx was removed. Fungal pseudoparenchyma in the base of the petals eventually formed sclerotia and microconidia. Large numbers of apothecia and sclerotia were frequently in the soil, below infected plants. Apothecia were nearly sessile or, when buried in soil, had stipes up to 40 mm in length. They also had saucer-like disks of 5 to 20 mm in diameter. Ciborinia camelliae was recovered consistently from infected petals, sclerotia, and spores collected from apothecia, then plated on potato dextrose agar amended with 100 mg of streptomycin sulfate per liter. Pathogenicity of three isolates was confirmed by inoculating flowers of potted camellia plants (cv. Waterhouse), with spores obtained from apothecia. Noninoculated plants served as controls. All plants were kept in a growth chamber at 20°C and kept moist. Inoculated plants developed symptoms within 12 days, whereas control plants remained symptomless. C. camelliae was reisolated from flowers of inoculated plants. Camellia flower blight was first observed in Japan, in 1919, then in the United States (1938), New Zealand (1993), and more recently in several European countries, including Italy (1999) (1). This report confirms the occurrence of camellia flower blight in Italy and apparently is the first report in which C. camelliae was isolated and pathogenicity tests completed. Reference: (1) C. H. Taylor and P. G. Long, NZ J. Crop Hortic. Sci. 28:123, 2000.