Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/1999
Publication Date: 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 sought 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 devised. This system was used to screen 84 bacterial seed treatments and four chemical treatments in the field over the entire growing season. Eight bacterial isolates and one experimental chemical treatment increased wheat shoot biomass significantly over the nontreated controls. No phytotoxicity was evident with any of the bacterial treatments. These eight isolates will be used alone or 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, Jackson, was planted at the Eastern Virginia Agricultural Research and Education Center at Warsaw, VA. with an Almaco cone planter configured for head row planting. Candidate bacterial strains were obtained from Gustafson, Incorporated, Novartis or isolated at this location from the roots of apparently healthy soft red winter wheat plants, cv. Jackson, growing within an area of the same field where plants with severe take-all symptoms and signs occur. Disease assessments were made at Zadoks' Growth Stage 41 and again at Zadoks' Growth Stage 60 on a 1 to 5 scale, where 1 = apparently healthy and 5 = plants severely stunted and prematurely killed. At the end of the growing season the total above ground biomass from a one meter section of each row was collected and weighed. Although all treatments involving wheat exhibited symptoms of take-all, one of the fungicide seed treatments, Experimental Chemical 1F, exhibited superior activity in suppressing the disease. No evidence of phytotoxicity was observed for any fungicide treatment or bacterial isolate. Eight of the bacterial isolates promoted biomass accumulation of one standard deviation greater than the mean for the experiment. These isolates, along with seven others, were identified by cellular fatty acid profiles and were selected for further study in the same field in the 1998-99 season. They are identified to genus, species, and isolate number. These isolates represent species from 8 different genera. They were used to treat Jackson wheat seed either alone or in combination (up to three isolates per treatment) and planted in Oct 98 using the same experimental design and procedures reported here.