GRAIN-YIELD RESPONSES OF WINTER-WHEAT COINOCULATED WITH CEPHALOSPORIUM-GRAMINEUM AND GAEUMANNOMYCES-GRAMINIS VAR TRITICI

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 less-than-or-equal-to 0.001) of C. gramineum inoculum on yield loss in all 5 yr, and a quadratic effect (P less-than-or-equal-to 0.01) in 2 of the 5 yr. For inoculum of G. g. tritici, there were linear and quadratic effects (P less-than-or-equal-to 0.001) all 5 yr. Additionally, a negative interaction (P less-than-or-equal-to 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.