INHIBITION OF OLIVE KNOT DISEASE BY POLYPHENOLS EXTRACTED FROM OLIVE MILL WASTE WATER
S. Krid, M. Bouaziz, M.A. Triki, A. Gargouri, A. Rhouma
Olive mill waste water (OMW) and phenolic extracts, used at different concentrations in vitro displayed a high level of antibacterial activity against Pseudomonas savastanoi pv. savastanoi, the causal agent of olive knot disease. In in planta experiments, phenolic compounds used at three concentrations (1000, 500 and 100 mg l-1) completely inhibited the formation of knots on twigs inoculated with pathogenic strains IVIA 1628 and Aw9. GC/MS analysis revealed the presence of hydroxytyrosol in high concentration, in addition to tyrosol, catechol, caffeic acid and p-coumaric acid, suggesting their antibacterial effect. Copper treatment was less effective than phenolic compounds since the inhibition percentages of knot formation were 6% and 12% for IVIA1628 and Aw9, respectively. These results show that phenolic compounds extracted from OMW and rich in hydroxytyrosol can be excellent substitutes of copper compounds for controlling olive knot disease.