Development of tools for studying Olea europaea: Pseudomonas savastanoi interaction

Abstract

Being one of world’s main olive oil producers, the culture of olive trees is of considerable importance for Portugal. One of the diseases that commonly affects Portuguese olive orchards' is the olive knot, caused by the bacteria Pseudomonas savastanoi (Pseudomonas syringae pv savastanoi), which leads to the appearance of tumours in the stems and leaves, drastically reducing the production of fruits. With the objective of developing an in vitro elicitation system we initiated suspension cell cultures from calli of the variety Galega Vulgar – which is known to be resistant to the infection. Cells in middle exponential growth phase were incubated with a suspension of P. savastanoi. XTT was used to quantify the perhydroxyl / superoxide (H2O./O2-) radical acid-base pair associated to the oxidative burst, during the time course of elicitation, allowing the evaluation of the Hypersensitive Response. The results showed the existence of two bursts (100 and 300 min after elicitation), which are characteristic of the HR that occurs in the incompatible interactions). By screening an elicitated O. europaea cDNA library, a clone encoding phenylalanine ammonia lyase (PAL) was obtained, and the coding region used as probe to evaluate Pal expression levels, during the time course of elicitation.