Recovery of Pseudomonas savastanoi pv. savastanoi from symptomless shoots of naturally infected olive trees

Abstract

Seasonal dynamics of Pseudomonas savastanoi pv. savastanoi (Psv) on stems and leaves from symptomless shoots of naturally infected olive trees was monitored in Spanish olive orchards. Data inferred from the comparison between washing of leaves and dilution-plating versus leaf printing of individual leaves suggested that Psv population sizes varied by over several orders of magnitude, among leaves sampled concurrently from the same shoot. We did not find significant differences between leaves and stems, in respect to the number of samples where Psv was isolated or detected by PCR, showing that Psv colonizes both leaves and stems. The frequencies of Psv isolation and average populations were highly variable among field plots. No correlation between Psv populations and those of non-Psv bacteria in any plant material or field plot was observed. However, where both Psv and yellow Pantoea agglomerans colonies were isolated a positive correlation was found. In a selected field plot, dynamics of Psv over three years showed significant differences between summer and the rest of seasons. The highest Psv population occurred in warm, rainy months, while low numbers were generally found in hot and dry months.