Symptom Variability and Selection for Reduced Severity of Cotton Seedling Disease Caused by Pythium ultimum. L. F. Johnson, Professor, Department of Entomology and Plant Pathology, University of Tennessee, Knoxville 37901-1071. G. K. Palmer, Graduate Research Assistant, Department of Entomology and Plant Pathology, University of Tennessee, Knoxville 37901-1071. Plant Dis. 69:298-300. Accepted for publication 25 October 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-298.

Hypocotyls of seedlings of cotton cultivars Auburn M, Coker 310, Delcot 277J, and Dixie King 3 were inoculated with Pythium ultimum. Selected plants were grown to maturity and self-pollinated; progenies were evaluated for disease severity. Variation in hypocotyl symptom expression among seedlings within cultivars did not differ among the four cultivars. Variation in symptom expression among seedlings of Auburn M was not reduced significantly among progenies through three successive generations of selection and self-pollination. A small but significant difference in susceptibility to P. ultimum between Delcot 277J and Coker 310 was established. This difference was apparent in the parent seedlings and in two succeeding generations of selection and self-pollination of resistant plants. Reduced disease severity was demonstrated in progenies of Auburn M. Third-generation seedlings of Auburn M were significantly more resistant than the cultivar parent.