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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #160235
Title: DELETERIOUS RHIZOBACTERIA FOR BIOLOGICAL CONTROL OF ANNUAL CROPPING WEEDS IN AUSTRALIA AND SOUTH KOREA

Author
item PELTZER, SALLY - W AUSTRALIA DEPT AGRIC
item LEE, SANG-BOK - RDA, SOUTH KOREA
item KREMER, ROBERT

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/26/2004
Publication Date: 2/9/2004
Citation: Peltzer, S.C., Lee, S., Kremer, R.J. 2004. Deleterious rhizobacteria for biological control of annual cropping weeds in Australia and South Korea [abstract] [CD-ROM]. Weed Science Society of America Meeting Abstracts. No. 79.

Interpretive Summary:

Technical Abstract: Deleterious rhizobacteria (DRB) are described as non-parasitic bacteria that are associated with plant roots and inhibit or reduce plant growth. These DRB usually inhibit growth by producing phytotoxins, but they can also reduce plant growth by competing with the plant for nutrients or indirectly by reducing the colonization of beneficial rhizobia or mycorrhiza. These DRB as biocontrol agents for weeds have received considerable attention in developing alternative weed management for reducing herbicide use and intensive tillage. Many of these DRB are very specific in their level of plant growth reduction; however, their specificity must be determined on a wide range of plant species prior to widespread release of the agents for use in crop production. Selected rhizobacteria cultured from Missouri, USA soils capable of suppressing seedling growth of selected weeds of U.S.A. cropping systems were evaluated for their effects on weeds and representative crops of cropping systems in Australia and South Korea. There were three types of assays: sterile agar plates, hydroponics system (sterile), and plant-soil bioassays (non-sterile). In agar plate assays, 3 of 4 DRB isolates reduced root growth of all crop cultivars and weed species from Australia; all DRB isolates reduced root growth of barnyardgrass (Echinochloa crus-galli) from Korea; and 3 of 4 isolates reduced rice root growth. DRB assayed in a hydroponics system showed reduced effects of DRB on crop species from Australia but significantly reduced root growth of Rice cv. Nongan from Korea. Rat's tail fescue (Vulpia myuros), soft brome (Bromus hordaceus) and barnyardgrass were inhibited by one or more DRB. Under non-sterile conditions, however, in plant-soil bioassays, canola (Brassica napus cv. Surpass 501) from Australia was the only crop with suppressed growth. Rat's tail fescue, ripgut brome (Bromus diandrus), and barnyardgrass growth were also inhibited by one or more DRB. Under non-sterile conditions, the isolates must compete with other microorganisms in the rhizosphere. This is the likely mechanism for DRB to reduce growth; different plants exude different chemicals into the rhizosphere affecting the type and magnitude of associated and competing microorganisms. This research suggests a need for selecting DRB in Australian and Korean environments to improve efficacy of biocontrol and decrease the risk of reduced crop production.