GENETICALLY ENHANCING THE EFFICACY OF PLANT PATHOGENS FOR CONTROL OF WEEDS

There are many plant pathogens that attack weeds, but only a few have proven virulent enough to control weed species and compete with chemical herbicides (R. E. McFayden, Annu. Rev. Entomol. 43, 369-393, 1998). One might surmise that there has been strong selection against highly virulent host-specific pathogens, as survival of the pathogen depends upon survival of the host. Total eradication of the host weed would not benefit the pathogen, an impasse that challenges researchers to develop innovative strate- gies using formulation, genetics, and synergy to enhance the effectiveness of biocontrol pathogens. Our research has capitalized on the inhibitory effects of certain amino acids on plant growth and development. Biocontrol pathogens that overproduce selected amino acids have increased virulence to the target weed and enhanced field performance. We report enhancement of virulence in three separate pathogen-host systems, two with Fusarium and one with Pseudomonas.