Title: An assessment of environmental conditions for control of downy brome by Pseudomonas fluorescens D7

Authors: A. Mark Ibekwe, Ann C. Kennedy, Tami L. Stubbs

Addresses: USDA-ARS, US Salinity Lab, 450 W. Big Springs Road, Riverside, CA 92507, USA. ' USDA-ARS, 215 Johnson Hall, Washington State University, Pullman, WA 99164, USA. ' Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164, USA

Abstract: Purpose: We evaluated the conditions that favoured Pseudomonas fluorescens strain D7 (P.f. D7) growth and inhibition of downy brome. Design/methodology/approach: Tn5 mutagenesis and a competitive assay were used to isolate mutants of P.f. D7. Isolates were screened for polysaccharide production and toxin response. Seven mutants were tested under varying pH, temperature and water potential and characterised using Random Amplified Polymorphic DNA analysis. Findings: Temperature, pH, and water potential did not affect weed suppression in bioassays, except at 37°C and with NaCl. Originality and/value: Understanding the genetics of P.f. D7 will help in the development of successful weed biocontrol systems.

Keywords: biological control; Pseudomonas fluorescens strain D7; Tn5 mutagenesis; downy brome; weed suppression; bioassays; weeds; weed biocontrol; weed control.

DOI: 10.1504/IJETM.2010.029959

International Journal of Environmental Technology and Management, 2010 Vol.12 No.1, pp.27 - 46

Available online: 03 Dec 2009 *

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