Pseudomonas tabaci . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Pseudomonas tabaci . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On at least 12 species of Nicotiana , as well as Capsicum annuum, Datura stramonium, Lycopersicon esculentum, Physalis grandiflora, Solanum melongena, S. nigrum and S. tuberosum (3: 611). Also infects plants belonging to numerous families, including some monocotyledons, when inoculated. The pathogen has been found naturally infecting various weeds (15: 613, 750), on the roots of weeds and crop plants without producing disease (21: 540) and associated with soyabean leaf pustule (29: 586: 35: 640). DISEASE: Wildfire of tobacco, a leaf spot. Chloroti spots appear and as they enlarge the centres become brown and dead and are surrounded by a wide chlorotic halo caused by the spread of a toxin into the adjacent tissue. Angular leaf spot, caused by P. angulata and does not produce the toxin shows no haloes. GEOGRAPHICAL DISTRIBUTION: Widespread in parts of Africa,. Asia, Europe, North and South America (CMI Map 293, 1954). Additional reports include those from Nyasaland (Malawi) (41: 7), Morocco (42: 631), U.S.S.R. (37: 738; 40: 51:), Belgium (34: 345), Greece (34: 108; 40: 649), Poland (41: 568). and Colombia (33: 82). TRANSMISSION: The pathogen can overwinter and be carried into new areas on seed, in soil and in unrotted plant material, particularly if dry (3: 105, 611, 612; 15: 179). It can also live saprophytically for long periods on the roots of various crops and weeds in the absence of tobacco (21: 540). The bacteria spread rapidly in water droplets in wet, windy weather (2: 345; 15: 537). Various other agents may spread the disease, particularly when plants are wet. The chewing of infected leaf by workers has also been suggested as a means of spread (3: 612).