Abstract
A description is provided for Erwinia carotovora var. atroseptica. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Solanum tuberosum. The occasional reports of other plants attacked mostly involve confusion of identity with other species of Erwinia. Of numerous reports in the Review of Plant Pathology since 1922, all are unlikely except the occurrences on Delphinium ajacis and lupin. Graham (1972) does record the examination of 8 isolates originating from other plants, 6 from UK, all of which could produce blackleg in potato, and 2 from Japan that could not. Five agglutinated with astroseptica antiserum, 3 did not. The origins were: Chinese cabbage and carrot in Japan, and tomato, cauliflower, Iris rhizome and water from cress beds in UK. Many plants are infected by artificial wound inoculation, but most show soft rot rather than blackleg symptoms. DISEASE: Blackleg of potato. Affected plants are usually stunted, with pale or yellowish leaves. Upper leaves are stiff and erect, and curl upwards at their margins. The stems near the soil level are black or dark brown and rotted; sticky but not softened. In prolonged wet weather plants may wilt and collapse rapidly. The seedpiece rots rapidly, and in severe attacks young tubers rot from the stem end. In milder attacks most tubers may appear healthy at harvest, only to rot in storage. Spread of the rot to healthy tubers in storage can cause severe losses. GEOGRAPHICAL DISTRIBUTION: Liable to be found in most places where potatoes are grown. CMI Map 131, ed. 3, 1973, lists 48 countries in all continents. TRANSMISSION: The disease is spread within an area and between areas in infected seed tubers that may appear healthy when planted. Tubers whose surfaces are contaminated with bacteria can also suffer infection either through wounds and growth cracks, or through the lenticels in the presence of free water, when cell proliferation is stimulated and ruptures the suberised plug at the lenticel opening. The bacteria do not penetrate the periderm directly. Transmission through the soil occurs at high inoculum and moisture levels (54, 4622), and the bacterium has been found to move with the ground water more than 3 m along a row away from infected seed tubers (51, 5e). Overwintering of the bacteria in soil is possible but varies between seasons and areas, and may not occur every season (30, 485; 53, 3597). Transmission by insects (54, 4624; 55, 5330) and by farm machinery (54, 4622) is also possible. In damp, poorly ventilated storage there is rapid spread directly from tuber to tuber. This can cause not only serious losses, but also widespread infection and contamination of seed potatoes for the following year.
Evaluation of different fungicides applied as seed tuber treatments for the control of potato silver scurf
