Root promoting compounds detected in olive knot extract in high quantities as a response to infection by the bacterium Pseudomonas savastanoi pv. savastanoi

Olive knot crude extract has been found to promote rooting in vitro of Koroneiki olive explants. The analysis of this extract revealed the presence of the naturally occurring auxins indole-3-acetic acid (IAA) and indole-3-acetonitrile (TAN) in high quantities. Both auxins were found in higher amounts in the knots, formed in olive shoots after the infection by the bacterium Pseudomonas savastanoi pv. savastanoi, than in healthy shoots. Further research showed that the knots were rich in phenolic compounds and odiphenols, as well as that they contained higher amounts of oleuropein (an o-diphenol) and another unidentified compound in contrast to healthy shoots. The analysis of polyamines showed higher concentrations of putrescine in the knots than in the healthy shoots, while it was not possible to detect any traces of spermidine or spermine in the olive knot extract. The results suggested a possible role and collaboration of auxins, phenolic compounds and polyamines, such as putrescine, in the root induction procedure of olive explants in vitro. Furthermore, a possible defense mechanism of olive tree against the bacterium was postulated, through the increased production of possible anticipins, like IAN and the unknown phenolic compound. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.