Phytophthora nicotianae causes blight of lily in Hungary

Hybrids of Lilium spp. have been grown on a large scale (1.2 ha) in greenhouses for cut flower production at a nursery in Dabas, a town 40 kms south-east of Budapest. In 2000, 10 to 20% of the plants of cultivars Stargazer and London were severely diseased. Some bulbs did not emerge while others developed a soft rot with lesions spreading from the base or middle of the stem into the leaves. The pathogen developing in diseased tissues appeared to be a Phytophthora species. It had aseptate hyphae and sporangia were papillate, both caducous and non-caducous, and their shape ranged from ovoid to elongate and distorted. The six isolates recovered from diseased plants and soil samples on selective media (Jeffers & Martin, 1986) looked very much alike. They developed white colonies with abundant aerial mycelia and had a maximum growth temperature of 36.5°C on pea-agar medium. Sporangia, 43.9±1.35 µm long and 33.2±0.8 µm wide, were non-caducous and ellipsoidal to ovoid in shape; distorted shapes were not observed in culture. Chlamydospores, 34.9±1.13 µm in diameter, were terminal or intercalary and formed singly. Oospores were not observed.

These characteristics were consistent with a heterothallic species such as P. nicotianae Breda de Haan (syn. P. parasitica) (Erwin & Ribeiro, 1996). Upon mating with an A1 type isolate of P. nicotianae, our isolates formed oogonia (23.3±0.65 µm in diameter), amphigynous antheridia 10.5±0.75 µm long and 11.0±0.52 µm wide and, eventually, aplerotic oospores 19.9±1.0 µm in diameter indicating that these isolates were the A2 mating type. Pathogenicity was confirmed by inoculating unwounded stem bases or leaves of both lily hybrids with zoospore suspensions. Symptoms and disease development were similar to those observed on naturally infected plants; cultivar London appeared to be more susceptible than Stargazer. Also, isolates were pathogenic on tomato following stem inoculation. PCR amplification of genomic DNAs using the P. nicotianae-specific primer pair ITS3-PNIC1 (Tooley et al., 1997), generated a 455-bp sequence, confirming that the pathogen was P. nicotianae. This is the first record of Phytophthora blight of lily in Hungary and possibly in continental Europe.