Full TGIF Record # 40890
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Publication Type:
i
Report
Author(s):Nelson, Eric B.; Van Dijik, Karin
Author Affiliation:Associate Professor, and Graduate Research Assistant, Department of Plant Pathology, 334 Plant Science Bldg., Cornell University, Ithaca, NY 14853
Title:Genetic basis of biological control in a bacterium antagonistic to turfgrass pathogens
Source:Cornell Turfgrass: Annual Report 1996-1997. August 1997, p. 9-13.
# of Pages:5
Publishing Information:[Ithaca], NY: Cornell University
Keywords:TIC Keywords: Pythium; Enterobacter cloacae; Biological control; Genetics; Pathogens; Antagonism; Disease control; Fatty acids; Clones
Abstract/Contents:"The main goal of our project on Enterobacter cloacae genetics has been to identify the genetic determinants for biocontrol traits in Enterobacter cloacae so that their role in the suppression of Pythium-incited diseases of turfgrasses can be specifically elucidated. However, in the last year, we have had to modify our objectives slightly because of recent findings on the nature of pathogenn suppression in this system. The current primary objectives of our studies are to 1) identify and clone genes involved in fatty acid metabolism in E. cloacae strain EcCT-501; 2) sequence fatty acid metabolic genes; 3) establish relationships between fatty acid metabolism and biological control of Pythium-incited diseases on creeping bentgrass. In 1996, we obtained several additional mutants. The most notable of these are strains 3-1 and 4-1 that fail to grow on media containing linoleic acid as a sole carbon source, but grow well on a minimal media containing succinate. This selection protocol was chosen to avoid selecting mutants with disrupted Krebs cycle enzymes. As with mutants V58 and 21-1, mutants 3-1 and 4-1 are unable to reduce the stimulatory activity of linoleic acid, seed exudate, and to protect bentgrass seedings from infection by P. ultimum. Subsequent complementation and sequence analysis has revealed that the mutation in strain 3-1 is in the fadAB operon, which encodes five structural genes central to the b-oxidation of fatty acids. While this mutant is severely debilitated in its ability to catabolize linoleic acid, it is not clear whether this mutation represents defiencies in linoleic acid transport or in linoleic acid utilization. Therefore, we feel that a search for fadL and fadD mutants are central to our work. We have spent considerable effort over the past year trying to sequence the entire fadAB operon. We currently have the entire region sequenced upstream of the transposon insertion whereas the downstream portion is nearly 80% sequenced. We are currently in the process of trying to generate fadL and fadD mutants to allow us to ask questions about the role of fatty acid transport and utilization in biological control processes. We currently feel we have strong laboratory evidence for the role of fatty acid metabolism in biological control processes with Pythium species on turfgrasses. Our work will focus over the next few years in trying to 1) determine whether these processes do indeed function in turfgrass soils; 2) further identify fadL and fadD mutants that will help us to distinguish between fatty acid uptake and utilization; 3) continue the sequencing of fatty acid genes; and 4) examine turfgrass species and varieties for fatty acid levels in seeds. The knowledge that the inactivation of fatty acid germination stimulants could be an important mechanism by which bacterial biocontrol agents interfere with pathogens may have an influence on the screening methods for effective biocontrol organisms, since organisms best capable of inactivating stimulants could be selected. Knowing that by interfering with the release of fatty acids by seeds, seeds might be less susceptible to certain soilborne pathogens, breeding programs for seeds other than those described above can incorporate low fatty acid seed content as a favorable screening criterion."
Language:English
References:0
Note:Tables
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Nelson, E. B., and K. Van Dijik. 1997. Genetic basis of biological control in a bacterium antagonistic to turfgrass pathogens. Cornell Turfgrass Ann. Rep. p. 9-13.
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