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Disease Note

An Unusual Phytophthora Associated with Root Rot of Subterranean Clover. P. A. Taylor, Irrigation Research Institute, Tatura, Victoria 3616. Australia. Plant Dis. 68:450. Accepted for publication 31 January 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-450e.

In 1982 a Phytophthora sp. was detected on rotted taproots of subterranean clover (Trifolium subterraneum L.) from irrigated pastures at widespread locations in northern Victoria, Australia. The fungus did not grow from roots onto PloVP agar or standard nonselective media. It was detected by microscopic observation of papillate sporangia and oospores produced on roots in distilled water. In pathogenicity tests, plants inoculated with zoospores developed taproot rot and the Phytophthora was detected on the root lesions. Isolates on clover seedlings inoculated with single sporangia were morphologically indistinguishable from the parent, with papillate sporangia, markedly aplerotic oospores, and both amphigynous and paragynous antheridia. This combination of characters is apparently unique in the genus and suggests the fungus may be a new species. Isolates have been lodged at the Commonwealth Mycological Institute (IMI 278933).
References: Newhook, F. J., et al. Mycol. Pap. 122, 1978. Waterhouse, G. M. Mycol. Pap. 92, 1963.