Virulence and indole-3-acetic acid (IAA) biosynthesis ability of Turkish Pseudomonas savastanoi pv. savastanoi isolates and susceptibility of some native olive genotypes
Aim of study: To evaluate the virulence and indole-3-acetic acid (IAA) biosynthesis ability of several Turkish P. savastanoi pv. savastanoi isolates and the susceptibility of some native genotypes to olive knot. Area of study: The Aegean, Marmara, and Mediterranean Regions of Turkey. Material and methods: 101 isolated bacteria were identified on the basis of biochemical, PCR for amplification of the bacterial iaaL gene, and pathogenicity tests. The virulence of the isolates was determined in a randomized experimental trial carried out by stem inoculation of pot-grown seedlings of olive (cv. ‘Manzanilla’) in the growing chamber. The amounts of IAA produced by the isolates were determined colorimetrically. The susceptibility of native olive genotypes was evaluated on 2-yr old plants inoculated with two distinct strains. Main results: Tested P. savastanoi pv. savastanoi isolates showed significant differences in virulence found to be associated with their geographical origin. The isolates produced IAA amounts varied from 148.67 to 0.3 μg mL-1. The geographical variation in IAA biosynthesis ability of the isolates was observed. No correlation (R=0.0225) was determined between virulence and IAA amounts of the isolates. Native olive genotypes indicated different susceptibility levels to the olive knot pathogen. No genotype tested had complete resistance. However, low susceptible genotypes (‘Memecik’, ‘Ayvalık’ and ‘Uslu’) were identified. Some genotypes had variable reactions depending on the isolate used. Research highlights: The results undergird the differences in the virulence and IAA production of the isolates within the area and also between geographical locations. Genotypes with low susceptibility can be used as genitors in further breeding studies.