Reduction in Pycnidial Coverage After Inoculation of Wheat with Mixtures of Isolates ofSeptoria tritici

Inoculation of wheat seedlings with certain combinations of isolates of Septoria tritici resulted in marked reductions in pycnidial coverage of leaves compared with plants inoculated separately with individual components of the mixture. The effect was greater when the isolates were grown together than when grown separately and mixed before inoculation. The suppression of pycnidial formation did not depend on the ratio of the isolates in the mixtures. The addition of a culture filtrate from one isolate to the conidial preparation of another isolate resulted in marked symptom suppression