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Disease Note Root and Stem Rot on Greenhouse-Grown Cowpea Caused by Phytophthora vignae in Sri Lanka. B. Sivakadadcham, Division of Plant Pathology, Central Agricultural Research Institute, Gannoruwa, Peradeniya, Sri Lanka. W. G. D. Fernando, Division of Plant Pathology, Central Agricultural Research Institute, Gannoruwa, Peradeniya, Sri Lanka. Plant Dis. 75:215. Accepted for publication 31 July 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0215A. In 1985 and 1986, cowpea (Vigna unguiculata (L.) Walp. subsp.
unguiculata 'Blackeye') grown in riverbank soil in greenhouses at
C.A.R.I. Gannoruwa, Sri Lanka, showed lower stem and root rot
and wilt that severely damaged or killed plants. A Phytophthora sp.
isolated from stem and root lesions was identified as P. vignae Purss
(1). Inoculum of the fungus was grown for 3 wk in autoclaved loam
soil and washed sand amended with cornmeal (3%, w/v), then was
added (1%, v/v) to pasteurized soil planted with Blackeye cowpea.
Koch's postulates were confirmed when root, stem, and wilt symptoms
were reproduced and the pathogen was reisolated from lesions.
Sporangia typical of P. vignae formed within 48 hr in Petri's solution.
Oogonia and oospores formed when the fungus was grown on cowpea
agar. This is the first report of P. vignae in Sri Lanka and suggests
that the pathogen may be present in cowpea fields of Sri Lanka. |