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Inhibition of Downy Brome (Bromus tectorum) Root Growth by a Phytotoxin from Pseudomonas fluorescens Strain D7

Published online by Cambridge University Press:  12 June 2017

Patrick J. Tranel
Affiliation:
Dep. Crop Soil Sci., Washington State Univ., Pullman, WA 99164
David R. Gealy
Affiliation:
USDA, Agric. Res. Serv., 215 Johnson Hall, Washington State Univ., Pullman, WA 99164
Ann C. Kennedy
Affiliation:
USDA, Agric. Res. Serv., 215 Johnson Hall, Washington State Univ., Pullman, WA 99164

Abstract

Field applications of the rhizobacterium, Pseudomonas fluorescens strain D7 (D7), have selectively suppressed downy brome in winter wheat test plots. A phytotoxin produced by D7 inhibits downy brome root growth. An assay system was developed for future investigations of the mechanism of action of this and other phytotoxins that inhibit root growth. A crude preparation of the phytotoxin, cell-free supernatant (CFS), had little activity on downy brome root elongation in a sand-petri plate system. CFS was very active in a hydroponic system, in which a 6% (v/v) concentration inhibited root elongation within 1.5 h. Inhibition of root elongation was reversible in this system. Root elongation of downy brome seedlings resumed within 3 h after removal from a 9-h incubation in 8% CFS. CFS from genetic variants of D7 did not substantially inhibit root growth and a semi-crystallized precipitation product from D7 CFS inhibited root growth similarly to D7 CFS, indicating that the phytotoxin present in the CFS was responsible for growth inhibition.

Type
Research
Copyright
Copyright © 1993 by the Weed Science Society of America 

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