Characterization and variability of strains of Xanthomonas axonopodis pv. passiflorae from the state of Pará, Brazil

Abstract

Bacterial spot, caused by Xanthomonas axonopodis pv. passiflorae, is a disease that has limited the cultivation of passionfruit in various orchards in Brazil. The objective of this work is to characterize and evaluate the variability of 29 strains of X. axonopodis pv. passiflorae from different municipalities producing yellow passionfruit in the state of Pará. The characterization was performed by the biochemical methods of KOH solubility, oxidase and Bactray, and the molecular methods of Xapas-F, Xapas-Ri and Xapas-Ro primers. The variability was evaluated by pathogenicity test and RAPD (randomly amplified polymorphic DNA). The strains of X. axonopodis pv. passiflorae were Gram-negative and oxidase-negative, and tests with the Bactray kit showed no relation between the collection municipality and group composition. The Xapas-F/Ri/Ro primers were specific for the strains. The primers used amplified 118 polymorphic bands in the RAPD reactions and the highest genetic similarity was between the strains PA15 and PA16. As the pathogenicity test evidenced a pathogenic variability, the strains PA2.1, PA4.5, PA14, PA4.2, PA4.1, PA4.6, PA3.4 and PA4.3 present the highest severity values for the disease. The strains of X. axonopodis pv. passiflorae show characteristics typical of the species, and genetic and pathogenic variability among them.