USE OF MIXTURES OF FLUORESCENT PSEUDOMONADS TO SUPPRESS TAKE-ALL AND IMPROVE THE GROWTH OF WHEAT

Fluorescent Pseudomonas strains were tested alone and in combinations for the ability to suppress take-all in greenhouse and growth chamber tests and to enhance the growth and yield of wheat in fields infested with Gaeumannomyces graminis var. tritici. In general, certain combinations of strains enhanced yield, whereas other mixtures and strains used individually did not. Overall, the best combinations were Q2-87 plus Q1c-80 plus Q8d-80 plus Q65c-80, Q2-87 plus Q1c-80 plus Q8d-80 plus Q69c-80, and Q1c-80 plus Q8d-80 plus Q65c-80. For example, in a field test on spring-sown wheat at Pullman, WA, during 1989, the treatment Q2-87 plus Q1c-80 plus Q8d-80 plus Q65c-80 significantly (P = 0.05) increased yield 20.4% compared to a nontreated control, whereas each strain used individually had no significant effect on yield. This work demonstrates the potential benefits of using combination treatments to suppress take-all and suggests the importance of additive and interactive effects among introduced bacteria in biological control.