Fusarium oxysporum Causing Leaf and Stem Blight of Jacquemontia tamnifolia in Alabama. M. A. Crawford, Department of Plant Pathology and Alabama Agricultural Experiment Station, Auburn University, Auburn 36849. G. Morgan-Jones, Department of Plant Pathology and Alabama Agricultural Experiment Station, Auburn University, Auburn 36849. Plant Dis. 72:268. Accepted for publication 1 October 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0268A.
Smaliflower morningglory (Jarquemonila tamifolia(L) Griseb.) is
an annual weed commonly found in the southeastern United States. During October 1986, in Henry County, Alabama, numerous J. tamnifolia plant were found with circular leaf spots and stem lesions bearing peach-colored sporodochial. Isolations from symptomoatic stems yeild cultures of Fusariam oxysporum Schlecht. and F. equisetti. (Corda) Sacc. Pathogeniity tests were conducted in the greenhouse by spraying spore suspensions of 16-day-old cultures of each fungus on 8-wk-old J. tamnifolia plants. Only those plants inocultated with F. oxysporum developed symptoms like those observed in the field. Symptoms developed within 7 days of incoculation, and conidiation occurred on the lesions after 12 days. No wilt symptoms were observed in either the rield or the greenhouse inoculation studies. The implicated fungus appears to differ from F. o. f. sp. baratas (Wr.) Snyd. & Hans., a known wilt-inducing pathogen of sweet potato (Ipomoea batatas (L.), a close relative of J. tamnifolia within the Convolvulacaee. Previous work on weed hosts of fungi causing diseases of sweet potato indicated J. tamifolia to be a symptomless carrier of F. o. f. sp. batatas (1). Without pathogenicity tests on sweet potato however, we cannot be certain that the biotype cuasing leaf and stem blight of J. tamifolia is a separate entity.