Induction of systemic resistance (ISR) by plant growth promoting rhizobacteria was tested against eucalypt (Eucalyptus spp.) rust caused by Puccinia psidii. Nearly 80 day old cuttings, previously rooted in rhizobacteria-treated and untreated (control) substrate, were inoculated with a 2 x 10(4) P. psidii urediniospore/ml suspension. The inoculated plants were incubated in an intermittent mist growth chamber at 25 ºC, in the dark for 24 h. Subsequently, the plants were maintained at 22 ºC and 12 h photoperiod at 40 mmoles (photons).s-1.m-2 light intensity. A completely randomized design with four replications and four plants each was used. After 13 days of inoculation, the mean number of pustules/leaf, number of uredinias/sample and the mean number of spores produced/uredinia were scored. Among the rhizobacterial isolates tested, FL2 and MF4 were significantly more efficient in reducing rust severity. This test was repeated and the same trend was found. These two best rhizobacterium isolates were not as efficient in reducing rust infection when inoculated on the same clone seven days before inoculation as they were when cuttings were rooted in rhizobacterial treated substrate.
cloning; cutting; PGPR's; systemic resistance induction
