Pineapple lily (Eucomis vandermerwei) is grown for its exotic-looking flower spike that looks like a small pineapple. It is used as an accent plant in the garden or for its long-lasting cut flowers. In late November 2007, plant foliage was submitted to the California State Diagnostic Laboratory by a commercial grower for phytosanitary inspection before shipment of bulbs to Europe. Leaves had wet, brown, elliptical spots of 1 to 2 cm long, some with yellow halos. The interior of the older spots was pale brown and papery. Conidiophores typical of Botrytis spp. were observed on the abaxial side of the leaf in the interior of the older spots. Isolations on half-strength acidified potato dextrose agar (APDA) yielded a grayish mycelium with conidiophores developing on the plant tissue only. The agar was grayish yellow, especially when viewed from the underside. Conidiophores measured 275 to 650 μm × 15 to 20 μm (411.2 × 15.5 μm average). Conidia were light brown, subglobose to broadly ellipsoidal, and measuring 10 to 15 × 13 to 20 μm (11.8 × 16.2 μm average). Scattered, black sclerotia measuring 335 to 1,007 × 518 to 1,079 μm (668.9 × 743.9 μm average) formed on the medium after approximately 7 days. Pathogenicity was confirmed by inoculating four Eucomis spp. plants with one inoculation per leaf, four leaves per plant. Each leaf was wounded with a sterile pushpin and three agar plugs from 4-day-old cultures were placed in a plastic screw-cap lid filled with sterile water and clipped onto each wound. Plants were misted with water, covered with a plastic bag, and placed in a growth chamber at 16°C (12-h photoperiod) for 48 h after which the agar plugs and caps were removed. An equal number of plants were wounded and mock inoculated with APDA. Pathogenicity experiments were repeated. After 14 days, all inoculated leaves had lesions and the fungus was reisolated. No Botrytis spp. were isolated from the mock-inoculated plants. Our sequence of the intergenic spacer regions of one isolate, GenBank FJ10809, matched Botrytis hyacinthi sequence AJ716297 with 99.8% identity. Using molecular (3) and morphological characters (1,4), the pathogen was identified as B. hyacinthi, the cause of fire disease in hyacinths. This pathogen was described previously on hyacinths in Washington State (2), the Netherlands (4), and the United Kingdom (2). The importance and economic impact of this disease appears to be limited because it has only been observed on mature or senescing foliage and not bulbs. To our knowledge, this is the first report of B. hyacinthi causing a leaf spot on pineapple lily.
References: (1) C. J. Gould et al. Plant Dis. Rep. 42:534, 1958. (2) W. C. Moore. Page 14 in: Diseases of Bulbs. Bull. No. 117. Minist. Agric. Fish. London, 1939. (3) M. Staats et al. Mol. Biol. Evol. 22:333, 2005. (4) J. Westerdijk and F. H. Van Beyma Thoe Kingma. Meded. Phytopathol. Lab. “Willie Commelin Scholten” 12:15, 1928.
