Erwinia amylovora: the molecular basis of fireblight disease

Taxonomy: Bacteria; Proteobacteria; g subdivision; order Entero-bacteriales; family Enterobacteriaceae; genus Erwinia. Microbiological properties: Gram-negative, motile rods. Related species: E. carotovora (soft-rot diseases), E. chrysan-themi (soft-rot diseases), E. (Pantoea) stewartii (Stewart's wilt of corn), E. (Pantoea) herbicola (epiphyte). Host range: Affects rosaceous plants, primarily members of the Pomoideae. Economically important hosts are apple and pear. The commercial implications of fireblight outbreaks are aggravated by the limited effectiveness of current control measures. Disease symptoms: E. amylovora infection is characterized by water soaking of infected tissue, followed by wilting and tissue necrosis. Necrosis gives tissue a scorched, blackened appearance, giving rise to the name fireblight. Symptoms are often localized to blossom bracts or young shoots but, in highly susceptible hosts, can spread systemically resulting in death of the entire tree. Infections can vary in severity depending on climatic conditions and host susceptibility. Useful web site: http://www.agric.gov.ab.ca