VIEW ARTICLE

Resistance

Generation Mean Analysis and Heritabilities of Resistance to Septoria tritici in Durum Wheat. Maarten van Ginkel, Former graduate student, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, Montana State University, Bozeman 59717, Present address: CIMMYT, Londres 40, Apdo, Postal 6-641, Deleg. Cuahtemoc, 06600 D.F., Mexico; Albert L. Scharen, Research plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, Montana State University, Bozeman 59717. Phytopathology 77:1629-1633. Accepted for publication 28 May 1987. 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, 1987. DOI: 10.1094/Phyto-77-1629.

Thirteen durum wheats used in breeding programs in North Africa and the Middle East were crossed in all combinations except reciprocals. Backcrosses were made and generations P₁, P₂, F₁, F₂, BC₁, and BC₂ were tested as seedlings in the greenhouse. Seedlings were quantitatively inoculated with an isolate of Septoria tritici at the second-leaf stage, and the percentage of necrotic tissue of the first leaf was assessed 21 days later. Additive, dominance, and epistatic gene effects were estimated by a generation mean analysis on each of the 65 crosses. Significant additive and dominance gene effects were found in about one-half and one-third of the crosses, respectively. Estimates of broad-sense heritability ranged from 0 to 78%, with a mean of 38%. The proportion of variance explained by models generally involving only additive and dominance gene effects, was R² ≥ 0.88. Thus, we concluded that epistatic effects were of minimal importance. The additive gene effects component was of prime importance, but the dominance component also was often significant. We found heritability estimates to be of an intermediate magnitude and thus conclude that selecting for resistance to S. tritici on a single-plant basis could be successful but probably slow.