Abstract
IN her work on South African Erysiphaceae, Doidge1 has provisionally identified the powdery mildew fungus that causes a troublesome disease on Cucurbitaceae throughout the country as Erysiphe cichoracearum DC. After two different mildew fungi were found to attack cucurbits in Europe2, Doidge3 realized that this identification should be regarded as tentative, but because the perithecial stage of the fungus had not been found in South Africa, more precise identification was considered impossible. Since then, a number of publications have appeared which have pointed out that it is possible to distinguish between the two fungi in question, namely Erysiphe cichoracearum DC. ex Merat emend. Salmon and Sphaerotheca fuliginea (Schlecht. ex Fries) Poll., on the basis of their conidial characteristics4–7. The conidia of the Sphaerotheca species contain conspicuous discoid or rod-shaped fibrosin bodies which were first observed and described by Bouwens8. They can be clearly seen if the spores are microscopically observed in a 3 per cent aqueous potassium hydroxide solution as recommended by Kable and Ballantyne7. In the conidia of E. cichoracearum, however, these bodies are lacking. Though both species produce conidia in long chains, the way in which the conidia germinate also differs. The germ tubes of E. cichoracearum are all simple and straight, but among those of S. fuliginea a number occur that are forked.
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References
Doidge, Ethel M., Trans. Roy. Soc. S. Afr., 5, 237 (1915).
Blumer, S., Beitr. Kryptog. Flora Schweiz., 7, 412 (1933).
Doidge, Ethel M., Bothalia, 5, 117 (1950).
Ballantyne, Barbara, Austral. J. Sci., 25, 360 (1963).
Boerema, G. H., and Van Kesteren, H. A., Neth. J. Plant Path., 70, 33 (1964).
Clare, B. G., Austral. J. Sci., 20, 273 (1958).
Kable, P. F., and Ballantyne, Barbara J., Pl. Dis. Reptr., 47, 482 (1963).
Bouwens, Henriette, Meded. Phytopath. Lab. Willie Commelin Scholten, 8, 3 (1924).
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GORTER, G. Powdery Mildew Fungus on Cucurbits in the Transvaal Province of South Africa. Nature 209, 938 (1966). https://doi.org/10.1038/209938a0
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DOI: https://doi.org/10.1038/209938a0
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