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In recent years, Chilean kiwifruit production has been affected by the phytopathogen Pseudomonas syringae pv. actinidiae (Psa), which has caused losses to the industry. In this study, we report the genotypic and phenotypic characterization of 18 Psa isolates obtained from Chilean kiwifruits orchards between 2012 and 2016 from different geographic origins. Genetic analysis by multilocus sequence analysis (MLSA) using four housekeeping genes (gyrB, rpoD, gltA, and gapA) and the identification of type III effector genes suggest that the Chilean Psa isolates belong to the Psa Biovar 3 cluster. All of the isolates were highly homogenous in regard to their phenotypic characteristics. None of the isolates were able to form biofilms over solid plastic surfaces. However, all of the isolates formed cellular aggregates in the air–liquid interface. All of the isolates, except for Psa 889, demonstrated swimming motility, while only isolate Psa 510 demonstrated swarming motility. The biochemical profiles of the isolates revealed differences in 22% of the tests in at least one Psa isolate when analyzed with the BIOLOG system. Interestingly, all of the isolates were able to produce indole using a tryptophan-dependent pathway. PCR analysis revealed the presence of the genes aldA/aldB and iaaL/matE, which are associated with the production of indole-3-acetic acid (IAA) and indole-3-acetyl-3-L-lysine (IAA-Lys), respectively, in P. syringae. In addition, IAA was detected in the cell free supernatant of a representative Chilean Psa strain. This work represents the most extensive analysis in terms of the time and geographic origin of Chilean Psa isolates. To our knowledge, this is the first report of Psa being able to produce IAA. Further studies are needed to determine the potential role of IAA in the virulence of Psa during kiwifruit infections and whether this feature is observed in other Psa biovars.

Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of a bacterial canker in kiwifruit plants and has caused economic losses worldwide. Currently, the primary strategies to control this pathogen include the use of copper-based compounds and even antibiotics. However, the emergence of isolates of Psa that are resistant to these agrochemicals has raised the need for new alternatives to control this pathogen. Bacteriophages have been proposed as an alternative to control bacterial infections in agriculture, including Psa. Here, we show the isolation and characterization of 13 phages with the potential to control Psa infections in kiwifruit plants. The phages were characterized according to their host range and restriction fragment length polymorphism (RFLP) pattern. Four phages were selected according to their lytic effect on the bacteria and their tolerance to different environmental conditions of pH (4–7), temperature (4–37 °C), and solar radiation exposure (30 and 60 min). The selected phages (CHF1, CHF7, CHF19, and CHF21) were sequenced, revealing a high identity with the podophage of Psa phiPSA2. In vitro assays with kiwifruit leaf samples demonstrated that the mixture of phages reduced the Psa bacterial load within three hours post-application and was able to reduce the damage index in 50% of cases. Similarly, assays with kiwifruit plants maintained in greenhouse conditions showed that these phages were able to reduce the Psa bacterial load in more than 50% of cases and produced a significant decrease in the damage index of treated plants after 30 days. Finally, none of the selected phages were able to infect the other bacteria present in the natural microbiota of kiwifruit plants. These results show that bacteriophages are an attractive alternative to control Psa infections in kiwifruit plants.

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Resumen Objetivo Caracterizar las lesiones de ligamento patelofemoral medial (LPFM) y las lesiones osteocondrales luego de un primer episodio de luxación patelar (LP) en pacientes jóvenes. Métodos Se evaluaron un total de 91 resonancias magnéticas de pacientes menores de 18 años (edad promedio: 14,5 años), con un primer episodio de LP, en un único centro, entre 2008 y 2012. Se analizaron la ubicación y la extensión de la lesión del LPFM, y la ubicación y el tamaño de las lesiones osteocondrales. Resultados Se encontraron lesiones del LPFM en el 49,5% (45) de los casos, y se observaron roturas totales y parciales del LPFM en el 10,9% (10) y el 39,5% (36), respectivamente. De las roturas totales, el 70% (7) fueron en la inserción rotuliana, el 20% (2), en la inserción femoral, y el 10%, multifocales. De las lesiones parciales, el 72% fueron rotulianas, el 19,4%(7), femorales, y el 8,3% (3), multifocales. Las lesiones osteocondrales se encontraron presentes en el 38% (35) de los casos; el 62,8% (22) se localizaron en la rótula y el 34,2% (12) en el cóndilo femoral lateral, mientras que solo el 3% (1) fueron multifocales. Conclusión La lesión del LPFM se encontró en la mitad de los casos de nuestra muestra, y, de los casos de lesiones parciales, la inserción rotuliana es el patrón más común en pacientes esqueléticamente inmaduros que presentan una LP por primera vez. Más de un tercio de los niños con LP por primera vez tendrá una lesión osteocondral concomitante, principalmente en la rótula. Nivel de Evidencia Nivel III.