Prediction of Stewart’s Wilt Disease in Single and Three-Way Crosses in Maize. W. M. Forgey, Former Research Specialist, University of Missouri, Columbia 65211. M. H. Blanco, Plant Pathologist, O’s Gold Seed Company, Farmer City, IL 61842; L. L. Darrah, Research Geneticist, Agricultural Research Service, U.S. Department of Agriculture, and Associate Professor of Agronomy, University of Missouri; and M. S. Zuber, Professor of Agronomy, University of Missouri. Plant Dis. 66:1159-1162. Accepted for publication 16 March 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982. DOI: 10.1094/PD-66-1159.

Six inbred lines of maize (Zea mays)—B14A, B37, Mo17, N28, Va35, and 33-16—were used to produce the 15 possible single crosses (A × B) and the 60 possible three-way crosses [(A × B)C]. Inbred lines, single crosses, and three-way crosses were grown at two locations for 2 yr and inoculated with Erwinia stewartii. Disease ratings were made when 50% of the plants per plot had tasseled and again near physiological maturity. Disease ratings indicated that resistance to the pathogen was the result of additive genetic effects because the general combining ability mean square was 20 times greater than specific combining ability. Highly significant correlation coefficients were detected for observed and predicted disease ratings among the single and three-way crosses studied. A significant linear response was found for increased susceptibility to the bacterial wilt pathogen for the observed ratings with each substitution of an inbred (B14A, N28, and Va35) that was susceptible to the pathogen for a resistant one (Mo17, B37, and 33-16) in the pedigree of single or three-way crosses. Our results supported the hypothesis that disease development in three-way crosses of maize may be predicted from inbred and single-cross disease rating scores.

Keyword(s): corn.