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Title: FIELD EVALUATION OF SELECTED BACTERIAL ISOLATES AND SEED TREATMENT FUNGICIDES FOR THE CONTROL OF TAKE-ALL IN ROANE SOFT RED WINTER WHEAT IN VIRGINIA, 2001

Author
item STROMBERG, E - VIRGINIA TECH
item Roberts, Daniel
item LACY, G - VIRGINIA TECH
item Lohrke, Scott
item LI, W - HUBEI UNIV., PRC
item Buyer, Jeffrey

Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2002
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 74 bacterial seed treatments and 1 chemical treatment in the field over the entire growing season. Twelve bacterial seed treatments increased wheat grain fresh weight significantly over the nontreated control. Many of these bacterial seed treatments have provided suppression of Take-all in consecutive field trials. No phytotoxicity was evident with any of the bacterial treatments. These twelve bacterial seed treatments will be used 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: Take-all of wheat, caused by Gaeumannomyces graminis var. tritici (Ggt), results in severe economic losses in Virginia. Candidate bacterial strains for the suppression of Ggt were isolated from the roots of apparently healthy soft red winter wheat plants, growing within an area of the same field where plants with severe take-all symptoms and signs occurred. A field screening method was used to test of diverse bacterial isolates for suppression of Ggt under agriculturally-relevant conditions. Isolates tested were from the genera Acinetobacter, Arthrobacter, Bacillus, Cellulomonas, Chryseobacterium, Flavobacterium, Janthinobacterium, Kocuria, Methylobacterium, Microbacterium, Micrococcus, Paenibacillus, Pantoae, Pseudomonas, Streptomyces, and Variovorax. In addition, several isolates of unknown identity were tested. All strains were applied at a rate of 107 to 1010 colony-forming units (cfu) per seed except B. cereus isolate 00-19 which was applied at a rate of 106 cfu per seed. Seed treatments containing B. sphaericus 00-40, isolate 302-6 (unknown identity), B. cereus 00-56, P. mendocina 302-7c, P. chlororaphis isolate 98-61 + isolate 302-6, B. lentimorbus isolate 302-2c, and A. radioresistens isolate 00-2 all resulted in grain weights that were significantly greater (P < 0.05) than the gelatin + Ggt control. This collection of treatments and treatments containing P. fluorescens isolate 00-7, A. caccoaceticus isolate 00-23, B. lentimorbus isolate 99-16, and isolate 99-43 (unknown identity) all resulted in grain weights that were significantly greater (P < 0.05) than the non-treated seed + Ggt control. Several bacteria in these seed treatments have provided suppression of Ggt in previous field trials (isolates 302-2c, 302-6, 98-61, 99-16, 99-43).