Grain Yield Responses of Winter Wheat Coinoculated with Cephalosporium gramineum and Gaeumannomyces graminis var. tritici . W. W. BOCKUS, Professor, Department of Plant Pathology, Throckmorton Hall, Kansas State University, Manhattan 66506-5502. M. A. DAVIS, Research Assistant, and T. C. TODD, Research Plant Pathologist, Department of Plant Pathology, Throckmorton Hall, Kansas State University, Manhattan 66506-5502. Plant Dis. 78:11-14. Accepted for publication 27 September 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0011.

Winter wheat (Triticum aestivum) was coinoculated at planting with one of four levels of inoculum of Cephalosporium gramineum and/or Gaeumannomyces graminis var. tritici in all possible combinations during each of 5 yr in the field. Response-surface models of the data were generated that described the effect of the interaction of the two pathogens on grain yields. There was a linear effect (P ≤ 0.001) of C. gramineum inoculum on yield loss in all 5 yr, and a quadratic effect (P ≤ 0.01) in 2 of the 5 yr. For inoculum of G. g. tritici. there were linear and quadratic effects (P ≤ 0.001) all 5 yr. Additionally, a negative interaction (P ≤ 0.01) occurred between inoculum levels of the two fungi in all 5 yr. These data indicate that, when the two organisms occur simultaneously in a field, they can compete slightly with each other as pathogens of the wheat host.

Keyword(s): Cephalosporium stripe, pathogen interactions, take-all