A new and simple pathogenicity test using carrot slices for Pseudomonas savastanoi pv. savastanoi, causal disease agent of olive knot

Abstract

Olive knot disease caused by Pseudomonas savastanoi pv. savastanoi is one of the important problems in olive (Olea europaea L), pomegranate (Punica granatum L.), myrtus (Myrtus communis L.) and jasmine (Jasminum officinale L.) in Hatay province, Turkey. The disease agent causes young seedling mortalities in intensive infections. The pathogenicity tests on the host plant seedling takes a long time to confirm identity and virulence of isolates/strains. In this study, we focused on a new and rapid pathogenicity test method for P. s. pv. savastanoi isolated from olive, pomegranate, myrtus and jasmine plants using carrot slices. Following inoculation of carrot slices with P. s. pv. savastanoi isolates, first typical knots were observed within a week and the knots fully developed on carrot slices 14 days after inoculation. Bacterial isolates were re-isolated from carrot slices and re-identified as P. s. pv. savastanoi using LOPAT tests, MALDI-TOF MS and molecular methods. One-year-old olive seedlings (cv. Gemlik) were inoculated with the re-isolated P. s. pv. savastanoi MKUBK-HZP14 for confirmation of carrot slice inoculation results. Typical knot symptoms were observed 60 days after inoculation of olive seedlings. The findings showed the carrot slice method to be a very simple and rapid technique for testing pathogenicity of P. s. pv. savastanoi isolates. The main advantage of this technique was found to be its sensitivity and promptness which yields correct results within 14 days.