Control of Olive Knot Disease with a Bacteriocin

A bacteriocin produced by Pseudomonas syringae pv. ciccaronei, used at three purification levels and several concentrations, inhibited the multiplication in olive tissues of P. s. subsp. savastanoi, the causal agent of olive knot disease and affected its epiphytic survival on leaves and twigs of olive plants. We determined that 6,000 Active Units ml−1 of crude bacteriocin, obtained by a simple purification step, is a concentration suitable to obtain an effective reduction of olive knot formation. Moreover, treatments of olive phylloplane with 6,000 AU m1−1 of crude bacteriocin were able to prevent bacterial multiplication by controlling the epiphytic survival of the pathogen. The inhibitory effect lasted until the end of observation (30 days). P. s. pv. ciccaronei bacteriocin, purified by ammonium sulphate precipitation, membrane ultrafiltration, gel filtration and gel electrophoresis when analysed by SDS-PAGE revealed three protein bands with molecular weights of 76, 63 and 45 kDa, respectively.