BIOLOGY, BIOLOGICAL CONTROL, AND MOLECULAR GENETICS OF ROOT DISEASES OF WHEAT, BARLEY AND BIOFUELS BRASSICAS
Location: Root Disease and Biological Control Research
Title: BIOLOGY, BIOLOGICAL CONTROL AND MOLECULAR GENETICS OF ROOT DISEASES OF WHEAT AND BARLEY. BIOLOGY, BIOLOGICAL CONTROL AND MOLECULAR GENETICS OF ROOT DISEASES OF WHEAT AND BARLEY.
Submitted to: Journal of Plant Pathology
Publication Type: Abstract Only
Publication Acceptance Date: August 20, 2008
Publication Date: August 20, 2008
Citation: Mavrodi, D., Mavrodi, O., Bonsall, R., Paulitz, T.C., Okubara, P.A., Schroeder, K.L., Kwak, Y., Weller, D.M. 2008. Biology, biological control and molecular genetics. Vol. 90 (2 Supplement) Aug. 2008 S 2.18. of root diseases of wheat and barley. biology, biological control and molecular genetics of root diseases of wheat and barley. . Journal of Plant Pathology.
Root diseases cause billions of dollars annually in losses to cereal growers. Resistance to foliar diseases is common, but resistance to root diseases is rare. Soilborne pathogens of cereals are managed through crop rotation, tillage, and chemical seed treatments. However, plants also defend themselves by supporting rhizosphere microorganisms antagonistic to soilborne pathogens. One of the best examples of natural root defense is the spontaneous decline during monoculture of take-all of wheat or barley caused by Gaeumannomyces graminis var. tritici. Take-all decline results from the buildup of strains of Pseudomonas fluorescens that produce the antibiotic 2,4-diacetylphloroglucinol (DAPG). The robustness of this suppressiveness appears to be modulated by the genotype of the DAPG producer, the wheat variety, and the sensitivity of the pathogen to DAPG. Strains of Pseudomonas
that produce phenazine antibiotics are abundant in the Pacific
Northwest of the USA where cereals are grown under low rainfall,
and these strains may be involved in the suppression of root
diseases other than take-all. Pseudomonads involved in natural
suppression are excellent biocontrol agents and the basis of recombinant strains with enhanced biocontrol activity. The introduction of genes encoding the phenazine biosynthetic pathway
into the DAPG producer P. fluorescens Q8r1-96, a highly aggressive
root colonizer of wheat and barley, resulted in enhanced control
of Rhizoctonia root rot. Real-time PCR assays have made it
possible to rapidly determine the inoculum density of soilborne
pathogens and the population densities of natural microbial antagonists, giving growers new tools to manage root diseases.