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Title: FIELD EVALUATION OF SELECTED BACTERIAL ISOLATES AND SEED TREATMENT FUNGICIDES FOR THE CONTROL OF TAKE-ALL IN MADISON SOFT RED WINTER WHEAT, 2000

Author
item STROMBERG, E - VA POLYTECH & STATE UNIV
item Roberts, Daniel
item LACY, G - VA POLYTECH & STATE UNIV
item Dery, Pierre
item Buyer, Jeffrey

Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Take-all of wheat, caused by the soilborne fungal pathogen Gaeumannomyces graminis var. tritici, causes major yield losses in wheat in Virginia and other regions of the United States. Biological control measures are being developed due to environmental problems associated with chemical control measures. A screening system for the identification of bacterial isolates that suppress Take-all of wheat under field conditions was used to screen 110 bacterial seed treatments and 4 chemical treatments in the field over the entire growing season. Eight bacterial isolates and two chemical treatments increased wheat shoot biomass significantly over the nontreated controls. One seed treatment, containing the bacterium Pseudomonas putida SB40, has provided suppression of Take-all in three out of three field trials. No phytotoxicity was evident with any of the bacterial treatments. These eight isolates will be used alone and in combination with each other in the next field experiment. This information is useful to scientists and extension agents working toward the development of environmentally-safe control measures for Take-all of wheat.

Technical Abstract: The soft red winter wheat cultivar, Madison, was planted at the Eastern Virginia Agricultural Research and Education Center at Warsaw, VA with an Almaco cone planter configured for head row planting at a rate of 24 seeds per row foot. The experimental design was a randomized complete block of 118 treatments with six replications. Bacterial strains were isolated from this location from the roots of apparently healthy soft red winter wheat plants growing within an area of the field with severe Take-all symptoms. At the end of the growing season the total above ground biomass from a one meter section of each row was weighed. Disease assessments were made one week prior to harvest on a 1 to 4 scale, where 1 = apparently healthy and 4 = plants severely stunted and prematurely killed. There was a significant difference in shoot biomass within treatments between the inner and outer rows of the four row blocks. For this reason data were analyzed per treatment by inner rows only or by outer rows only. Eight bacterial isolates and two chemicals applied as seed treatments promoted biomass accumulation of one standard deviation greater than the mean for the nontreated control in either inner or outer rows. One bacterial isolate, Pseudomonas putida SB40, provided significant disease suppression, determined by above ground biomass, in this and two previous field trials. Five bacterial treatments and one chemical treatment had a disease assessment rating that was significantly lower than the control, indicating disease suppression, in inner rows or outer rows. Only one experimental chemical demonstrated significant disease suppression based on above the ground biomass and the disease assessment rating.