New Zealand Journal of Agricultural Research abstracts

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Rhizobacteria harmful to seedling growth in white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.)

S. U. SARATHCHANDRA
J. A. BROWN
N. R. COX

AgResearch
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand

Abstract  Eleven strains of rhizobacteria (eight Pseudomonas spp. and three Enterobacter spp.) isolated from the rhizoplanes of white clover (Trifolium repens L.) or perennial ryegrass (Lolium perenne L.) plants from New Zealand pastures, were tested in vitro for toxic metabolites that inhibit root growth. Ten strains of bacteria inhibited root growth of white clover seedlings, whereas only four strains inhibited root growth of perennial ryegrass seedlings. One of the most inhibitory strains was identified as Pseudomonas asplenii. The culture filtrates of three bacterial strains were tested for heat tolerance. Toxic activity was destroyed by autoclaving culture filtrates at 121deg.C but not by boiling. Twelve inhibitory bacteria, including three Klebsiella spp., three Enterobacter spp., and six Pseudomonas spp. were tested for their effects on seedling growth and nitrogen (N) fixation in white clover. Bacterial cultures were washed and added to white clover seedlings (with and without Bradyrhizobium leguminosarum bv. trifolii) in sand culture. One strain each of P. asplenii and P. syringae decreased (P < 0.01) seedling growth and N fixation indicating their ability to grow and produce the toxic metabolites in the rhizosphere of seedlings possibly utilising seedling root exudates.

Keywords  deleterious rhizobacteria; nitrogen fixation; Pseudomonas spp.; root growth inhibition; Rhizobium

New Zealand Journal of Agricultural Research, 1996, Vol. 39: 129-136

0028-8233/96/3901-0129 $2.50/0 (c) The Royal Society of New Zealand 1996

PDF file of entire paper: medium quality (579K); (scanned from paper original: notes about this process)

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