The Outbreak of Olive Knot Disease Pseudomonas savastanoi pv. savastanoi on Natural Hosts and Evaluation of Olive Cultivars Susceptibility to Infection

Samer Essa
General Commission For Scientific Agricultural Research-
Lattakia Research Center
Faculty of Agriculture, Damascus University

Abstract

The results of the field survey of 38 locations from middle and coastal regions showed that olive knot disease spreads basically in the coastal region. The incidence of infection was 0-100% with severity of 7-90%. The geographic factor greatly affected the outbreak of disease,  as it increased by the increase of the altitude of the location above sea level.
The biochemical and pathogencity tests revealed that 49 olive isolates, 7 oleander isolates, 8 myrtle isolates and 3 pomegranate isolates out of 112 isolates obtained from Lattakia and Tartous had the characteristics of the bacteria Pseudomonas savastanoi pv. savastanoi.
Crisscross infection showed that the isolates from olive, myrtle and pomegranate had infected all tested hosts (olive, oleander, myrtle and pomegranate) except one isolate from myrtle. Oleander isolates had infected olive, myrtle and   pomegranate.
We found differences in the susceptibility of the 16 olive cultivars when they were evaluated with the two isolates S60 and N9. The two isolates varied in their agressivity on the same cultivar. According to the results, the cultivars can be classified into four groups: the most susceptible (Salonic, Tremba, Nebally and Khokhi ), susceptible (Sorani, Frontoio, Zorzalina, Khdairy and Shatawi), moderately susceptible (Jlot, Shemlaly, Trelia, Kaissy and Doebli), and tolerant varieties (Kkrosadi and Lock).