First Report of Bacterial Canker Caused by Pseudomonas syringae pv. morsprunorum Race 1 on Cherry in Chile.

Chile is the main exporter of sweet cherries (Prunus avium), with a total of 228.6 thousand tons exported in the 2019-20 season, and a production from the Coquimbo to the Aysén region (http://www.iqonsulting.com/yb/). In January 2019, cherry trees from a commercial orchard located near Osorno city (40°37'S, 72°54'W), Region de Los Lagos, Chile, showed symptoms such as the presence of wood cankers, necrotic spots in leaves, and premature defoliation, with a mean disease incidence near 40%. Symptomatic leaves with necrotic spots were collected for analysis, from which all the necrotic spots were extracted by incision with a sterile scalpel, macerated in 30 mL of AFT buffer and subsequently, 100 µL of the suspension was plated on King's B (KB) agar and incubated for 48 to 72 h at 27°C, obtaining a total of two bacterial colonies identified as 7684.1 and 7684.2. Afterward, each colony was stroked in a new KB agar plate, incubated for 16 h at 27°C, and the obtained biomass was used in subsequent experiments. In KB agar, both colonies exhibited fluorescence under UV light and, according to the LOPAT method (Lelliott et al., 1966), they were gram negative, positive to levan and tobacco hypersensitivity tests and negative to oxidase, potato soft rot, arginine dihydrolase and gelatin tests, and were confirmed as Pseudomonas syringae. Then, the 16s and gyrB genes of each isolate were amplified by PCR, sequenced, and compared with the NCBI Genbank database (Weisburg et al., 1991; Sarkar and Guttman, 2004), finding a 99,93% genetic similarity (1064/1065) with a previously reported 16s sequence of a Pseudomonas syringae pv. morsprunorum (Psm) isolate (accession number CP026558.1), and a 99,69% (636/638) with a previously reported gyrB gene of Psm (accession number LC364094.1), respectively. Additionally, the closest pathovar different to morsprunorum aligned with our gyrB sequence was P. syringae pv. aesculin, with 97,8% of identity (624/638). Our sequences were deposited in Genbank with the accession numbers MN528473 (16s), MN535696 (gyrB) for 7684.1, and MN528474 (16s), MN535697 (gyrB) for 7684.2. To identify if the isolates correspond to Psm races 1 (Psm1) or 2 (Psm2), race-specific conventional PCRs and qPCRs assays were carried out using the specific primers described by Kaluzna et al., (2016), showing that the two isolates were positive to Psm1 in both PCR assays. Pathogenicity was tested by inoculating immature cherry fruitlets (cv. Sweetheart) with bacterial suspension at 108 CFU/mL. For each strain, ten fruitlets were inoculated by pricking with a sterile needle previously immersed in the bacterial suspension (Ruinelli et al., 2019). Sterile distilled water was used as negative control. Seven to fourteen days post-inoculation, necrotic and water-soaked brown lesions with yellow margins were observed on the fruits inoculated with bacterial strains. The pathogen was reisolated and confirmed as Pseudomonas syringae pv. morsprunorum by 16s and gyrB sequencing, and as race 1 by race-specific PCRs. Our results were confirmed by the National Plant Protection Organization, (Servicio Agrícola y Ganadero de Chile, SAG), generating the first report of Psm race 1 in Chile. Thus, SAG established new protocols for quarantine of absent pests in the national territory (Resol. N°3080, SAG, Chile), and an immediate phytosanitary program for Psm (Resol. Exenta N°8948/2019, SAG, Chile). In conclusion, our discovery contributes to the monitoring and control of the disease in Chile.

CXCL12a/CXCR4b acts to retain neutrophils in caudal hematopoietic tissue and to antagonize recruitment to an injury site in the zebrafish larva.

Neutrophils are a major component of the innate immune response and the most abundant circulating cell type in humans and zebrafish. The CXCL12/CXCR4 ligand receptor pair plays a key role in neutrophil homeostasis, controlling definitive hematopoiesis and neutrophil release into circulation. Neutrophils overexpressing CXCR4 respond by migrating towards sources of CXCL12, which is abundant in hematopoietic tissues. However, the physiological role of CXCL12/CXCR4 signaling during inflammatory responses remains unknown. Here, we show that zebrafish mutants lacking functional CXCL12a or CXCR4b show disrupted granulopoiesis in the kidney and increased number of circulating neutrophils. Additionally, CXCL12a and CXCR4b mutants display exacerbated recruitment of neutrophils to wounds and not to infections, and migrating neutrophils to wounds show increased directionality. Our results show that CXCL12a/CXCR4b signaling antagonizes wound-induced inflammatory signals by retaining neutrophils in hematopoietic tissues as a part of a balance between both inflammatory and anti-inflammatory cues, whose dynamic levels control neutrophils complex migratory behavior.

Transcriptome Analysis of Sweet Cherry (Prunus avium L.) Cultivar 'Lapins' upon Infection of Pseudomonas syringae pv. syringae.

Bacterial canker caused by Pseudomonas syringae pv. syringae (Pss) is responsible for substantial loss to the production of sweet cherry in Chile. To date, the molecular mechanisms of the Pss-sweet cherry interaction and the disease-related genes in the plant are poorly understood. In order to gain insight into these aspects, a transcriptomic analysis of the sweet cherry cultivar 'Lapins' for differentially expressed genes (DEGs) in response to Pss inoculation was conducted. Three Pss strains, A1M3, A1M197, and 11116_b1, were inoculated in young twigs, and RNA was extracted from tissue samples at the inoculation site and distal sections. RNA sequencing and transcriptomic expression analysis revealed that the three strains induced different patterns of responses in local and distal tissues. In the local tissues, A1M3 triggered a much more extensive response than the other two strains, enriching DEGs especially involved in photosynthesis. In the distal tissues, the three strains triggered a comparable extent of responses, among which 11116_b1 induced a group of DEGs involved in defense responses. Furthermore, tissues from various inoculations exhibited an enrichment of DEGs related to carbohydrate metabolism, terpene metabolism, and cell wall biogenesis. This study opened doors to future research on the Pss-sweet cherry interaction, immunity responses, and disease control.

Enteroparasitosis en niños de escuelas rurales y urbanas de Temuco, IX Región de Chile / Intestinal parasites in rural and urban school children from Temuco, IX Región, Chile

Se estudia la prevalencia de enteroparasitosis en escolares de enseñanza básica de zonas rural y urbana de Cautín; IX Región, Chile, mediante examen seriado de deposiciones (Método de Telemann Modificado) y Test de Graham. El examen de deposiciones se efectuó en 380 niños y permitió comprobar 74% de positivos a protozoos y helmintos intestinales entre escolares rurales y 71,4% en los urbanos. De los protozoos, G. lamblia apareció en el 32,1%, con mayor frecuencia entre los escolares rurales (39,8%) que entre los urbanos (25,1%); de los helmintos, A. lumbricoides fue encontrado en el 11,1%, con notoria diferencias entre los niños de zona rural (20,4%) que en los urbanos (2,5%). El Test de Graham fue efectuado en 355 escolares y reveló infección por E. vermicularis en el 52,6% de los de sector rural y 49,2% de los urbanos. Se concluye que las enteroparasitosis siguen constituyendo un severo problema de salud pública en la zona, por su alta frecuencia en escolares, teniendo directa relación con diferencias socioeconómicas y culturales que continúan persistiendo