Corynebacterium michiganense . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Corynebacterium michiganense [Clavibacter michiganensis] . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Lycopersicon esculentum and other species of Lycopersicon ; also on Cyphomandra betacea, Nicotiana glutinosa, Solanum mammosum, S. muricatum, S. nigrum, (S. douglasii ) and other species of Solanum . Natural infection on S. tuberosum has not been recorded. DISEASE: Bacterial canker of tomato. A vascular wilt disease in which splitting of the stems may occur with the formation of yellow or reddish-brown cavities in the pith. Corynebacterium michiganense is a phloem invader, causing wilt symptoms in its host most rapidly at high nutrient concentrations; and conversely, producing maximum development of canker at low nutrient concentrations (27: 394). 'Birds eye' fruit spots occur under some climatic conditions and are round, at first white, later with a light brown roughened centre surrounded by a white halo. Fruits are invaded through the vascular system and show in section a yellow discoloration of the placenta. GEOGRAPHICAL DISTRIBUTION: Widespread, including the U.S.A., where the disease was first described, Canada, Europe, Australia, New Zealand. Africa (including recently Northern and Southern Rhodesia, Kenya and South Africa), China and South America. (CMI Map 26). TRANSMISSION: A wound pathogen spread by cutting knives, or through damaged roots in the soil. Leaf trichomes are also known to be avenues of infection ( Phytopathology 52: 1306, 1962). Survives from season to season in soil containing diseased plant material. Fruit spotting is probably caused by rain splash or overhead irrigation water dripping from leaves and cankers. The pathogen is seed transmitted and the incidence of infection may reach 1% from this source (33: 507; 36: 793). Transplanting to the field from seed-bed soil contaminated with plant refuse often results in a stand with over 50% canker (33: 507).