Determination of bacterial leaf spot of lettuce caused by Pseudomonas viridiflava (Burkholder 1930) Dowson 1939 and the reactions of some lettuce cultivars

Abstract

Pseudomonas viridiflava (Burkholder 1930) Dowson 1939 is a multihost plant pathogenic bacterium all over the world and also in Turkey. The aim of this study was to identify the pathogenic bacteria causing the symptoms of water-soaked necrotic leaf spots, dark brown spots on leaves, tip burn of leaf in curly type lettuce (Lactuca sativa var. crispy) grown in the field conditions in Beypazarı region and to reveal the reactions of some lettuce cultivars against the bacteria. For this purpose, twelve isolates were obtained from 4 different locations. Pathogenicity tests were conducted on curly type lettuce and all isolates were found pathogenic on the host. Isolated bacteria were evaluated for Gram reaction, LOPAT tests, colony morphology on King’s Medium B and carbon sources utilization by VITEK-2 system and identified as Pseudomonas viridiflava. The 16S rDNA region of a selected isolate representing the similar isolates in all tests was sequenced for genetic confirmation and the obtained sequence was submitted to the GeneBank under the accession number MN_539659. The result of the obtained sequence was 99.75% similar to the respective reference sequence after BLAST analysis. Reaction of the three different widely produced lettuce types, iceberg, curly and romaine types, with ten varieties against the causative bacterial agent was evaluated and the difference between the varieties found significant statistically. In this study, P. viridiflava was detected in lettuce in Central Anatolia for the first time.