Evaluation of Stenotrophomonas maltophilia strain C3 for biocontrol of brown patch disease

Bacterial strains isolated from grass foliage were tested for inhibition of brown patch disease, caused by Rhizoctonia solani Kuhn, on detached blades and potted seedlings of tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31). Stenotrophomonas maltophilia strain C3 prevented growth of the fungus on leaf blades and reduced the severity of necrosis on seedlings. When strain C3 was tested on tall fescue cv. 'Kentucky 31' planted at three seeding densities, biological control was not achieved. When the strain was applied to field plots of six tall fescue cultivars, the severity of brown patch disease was reduced in one cultivar, but increased in another. A rifampicin-resistant mutant strain of C3 applied to four cultivars was recovered from all of the canopies at approximately 10(6) CFU/g foliage throughout the experiment. This population level is over 10-fold lower than that associated with effective antagonism under laboratory conditions. (C) 1998 Elsevier Science Ltd. All rights reserved.