Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/1994
Publication Date: N/A
Interpretive Summary: Root diseases are major yield-limiting factors in the production of food, fiber and ornamental crops. Take-all, caused by Gaeumannomyces graminis var. tritici (Ggt), is the most important root disease of wheat in the U.S. and worldwide. Interest in the use of microorganisms to suppress soilborne plant pathogens has increased dramatically in recent years because of trends in agriculture toward greater sustainability and public concerns about hazards associated with the use of synthetic chemical pesticides. Take-all can be biologically controlled by a variety of soil microorganisms including root-associated bacteria known as fluorescent pseudomonads. The purpose of this research was to assess whether mixtures of strains of fluorescent pseudomonads, applied as seed treatments, were more effective at suppressing take-all than individual strains. We found that certain mixtures of up to four strains were more effective at controlling take-all in both the greenhouse and the field than the same strains used individually. These results show that strain mixtures provide a means to increase the activity of a biocontrol treatment and to improve the consistence of performance from field to field and year to year. These findings are useful to ongoing efforts to develop commercially viable biocontrol agents for plant pathogens.
Technical Abstract: 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 individualy 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.