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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Fusarium oxysporum was the first of 9 species to be described in the section Elegans, established as one of the six sections of the genus Fusarium by Wollenweber in 1913. By 1935, when Wollenweber & Reinking published their monograph of the genus, the number of species, varieties and forms included in Elegans had grown to 40. Fusarium oxysporum, apart from being the most economically important member of the genus Fusarium, is also one of the most labile and variable species. This variation may be expressed as a series of morphological strains which may be reasonably stable and this led to Wollenweber and Reinking's acceptance, or proposal, of such names as F. bostrycoides, F. conglutinans, F. orthoceras, F. lini, F. bulbigenum, F. angustum, F. dianthi and F. vasinfectum as distinct species. Apart from the difficulty of separating these species, especially after maintenance for some time on artificial media, it was gradually realized that the selective pathogenicity of the Elegans isolates was not necessarily linked to the morphological variant designated by a species name such as 'bulbigenum' or 'vasinfectum'. In fact almost any of these strains may carry the specific pathogenic capabilities for a particular host, the related cultural appearance being more related to ecological and geographical considerations than to true species charamers. Considerations such as these led Snyder & Hansen (1940) to amend the description of Fusarium oxysporum to agree with that of the section (group) Elegans. This reduced all the other species in the section to synonyms of F. oxysporum. They then designated 25 forms of this species based on their pathogenic patterns and capabilities. Since then, many new formae speciales have been described; they have been listed and summarized by Gordon (1965) and by Messiaen & Cassini (1968). One exception to the inclusion of all species in the Elegans group as F. oxysporum is F. redolens (see CMI Description 27).


 
Description type:Non-original description 
Description:Fusarium oxysporum Schltdl.: Fr., emend. Snyder & Hansen, Am. J. Bot. 27: 6067, 1940.
= Fusarium oxysporum Schltdl., Flora berol. 2: 139, 1824.
= Fusarium angustum Sherb., 1915.
= Fusarium bostrycoides Wollenw. & Reinking, 1925.
= Fusarium bulbigenum Cooke & Massee, 1887.
= Fusarium conglutinans Wollenw., 1912.
= Fusarium orthoccras Appel & Wollenw., 1910.
= Fusarium vasinfectum Atk., 1892.
= Fusarium lini Bolley, 1901.
= Fusarium dianthi Prill. & Delacr., 1901.
Mycelium delicate white or peach but usually with a purple tinge, sparse to abundant then floccose, becoming felted and sometimes wrinkled in older cultures. Microconidia borne on simple phialides arising laterally on the hyphae or from short sparsely branched conidiophores, generally abundant, variable, oval-ellipsoid to cylindrical, straight to curved, 5-12 x 2,2-3,5 µm. Macroconidia sparse in some strains, borne on more elaborately branched conidiophores or on the surface of Tubercularia-like sporodochia, thin-walled, generally 3 (-5)-septate, fusoid-subulate and pointed at both ends, occasionally fusoid-falcate, with a somewhat hooked apex and a pedicellate base: 3-septate, 27-46 x 3-4,5 (-5) µm; 5-septate, 35-60 x 3- 5 µm; 6-7-septate, 50-66 x 3,5-5 µm. Sterile stromatic pustules pale or deep violet, forming in some isolates and resembling Gibberella-like perithecia. Chlamydospores both smooth and rough walled, generally abundant, forming both terminally and intercalary, generally solitary but occasionally formed in pairs or in chains.
Hosts: Pleurivorous in soil.
Disease: Fusarium oxysporum occurs chiefly as a soil saprophyte and appears to survive winter in the mycelial or chlamydospore state. Numerous strains of this species are serious wilt pathogens of many crop plants. These together with saprophytic strains have the ability to live almost indefinitely in soil with the result that normal rotational cropping is not a practical control measure. Because of the importance of many of these physiologic strains to the plant pathologist and because of the immense amount of research that has been carried out in relation to their control, separate description sheets have been prepared dealing with the history, distribution and control measures of certain 'formae speciales'.
Geographical distribution: world-wide.
Literature: Gordon, Can. J. Bot. 43: 1309-1318, 1965; Messiaen & Cassini, Annls Epiphyt. 19: 387-454, 1968; Snyder & Hansen, Am. J. Bot. 27: 64-67, 1940; Wollenweber, Phytopathology 3: 24-50, 1913; Wollenweber & Reinking, Die Fusarien, 355 pp., Berlin, Paul Parey, 1935.

 
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