Phytophthora Rot of Potatoes in Texas Caused by Phytophthora parasitica and P. cryptogea. M. P. Grisham, Assistant Professor, Texas A&M University, College Station 77843. R. A. Taber, Research Scientist, and L. W. Barnes, Extension Plant Pathologist, Texas A&M University, College Station 77843. Plant Dis. 67:1258-1261. Accepted for publication 23 May 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1258.

Phytophthora parasitica and P. cryptogea were isolated in Texas from potato tubers displaying pink rot symptoms. Pathogenicity tests confirmed that isolates of each species are capable of inducing pink rot. Three cultivars and five advanced breeding lines were susceptible to both species. Artificial inoculation of buds and stems with both species resulted in rotted bud pieces, reduced bud vigor, and stem lesions. Vegetative growth of P. parasitica is optimal in vitro at 33 C, whereas that of P. cryptogea is 23 C.

Keyword(s): Phytophthora erythroseptica, P. nicotianae var. parasitica, Solanum tuberosum.