Virulence factors analysis of native isolates of Xanthomonas albilineans and Xanthomonas sacchari from Tucumán, Argentina, reveals differences in pathogenic strategies

• Published in: Plant pathology Vol. 70; no. 5; pp. 1072 - 1084
• Main Authors: Mielnichuk, Natalia, Bianco, María I., Yaryura, Pablo M., Bertani, Romina P., Toum, Laila, Daglio, Yasmín, Colonnella, María Antonela, Lizarraga, Leonardo, Castagnaro, Atilio P., Vojnov, Adrián A.
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01.06.2021
• Subjects: Adhesion; Adhesive strength; biofilm; Biofilms; Cell adhesion; Cell adhesion & migration; Colonization; Endoglucanase; epiphytic; exopolysaccharide; Exopolysaccharides; Leaves; Oxidative stress; pathogen; Pathogenicity; Pathogens; Phenotypes; Scald; Sensitivity analysis; Signs and symptoms; Sliding; Species; Stomata; Strains (organisms); Sugarcane; sugarcane leaf scald; Survival; Swimming; Twitching; Virulence; Virulence factors; Xanthan; Xanthomonas; Xanthomonas albilineans
• ISSN: 0032-0862; 1365-3059
• DOI: 10.1111/ppa.13367

Xanthomonas albilineans (Xa) and X. sacchari (Xs) are both sugarcane pathogens. Xa is the causal agent of leaf scald disease, but there is limited information about the pathogenicity of Xs. The aim of this work was to study virulence factors of native strains of Xa (Xa32, Xa33, and XaM6) and Xs (Xs14 and Xs15) previously isolated from sugarcane with leaf scald symptoms, to gain insight into the biology of each microorganism. We analysed epiphytic survival, sensitivity to oxidative stress, extracellular degradative enzymes, cell motilities, exopolysaccharide (EPS) characteristics, cell adhesion, biofilm development, and control of stomatal regulation of the five strains. We observed that each species presented similar phenotypes for every factor analysed. Xa strains appeared to be more sensitive to oxidative stress and presented lower epiphytic survival than Xs. All strains presented endoglucanase activity; however, we could only detect protease and amylase activities in Xs strains. Swimming and sliding were higher in Xs, but twitching was variable among species. We also observed that only Xs strains produced a xanthan‐like EPS, presented a strong cell adhesion, and structured biofilm. We detected some intraspecific variations showing that higher amounts of EPS produced by Xs14 correlated with its higher sliding motility and its homogenous and more adhesive biofilm. In addition, EPSs of Xs14 and Xs15 presented differences in strand height and acetyl percentage. Finally, we found that strains of both species were able to interfere with stomatal aperture mechanism. All these differences could influence the colonization strategies and/or disease progression in each species. Xanthomonas albilineans and Xanthomonas sacchari found in sugarcane with leaf scald symptoms present differences in virulence factors production that influence epiphytic survival and stomata regulation.