The molecular mechanisms underlying fish tolerance to soybean meal (SBM) remain unclear. Identifying these mechanisms would be beneficial, as this trait favors growth. Two fish replicates from 19 experimental families were fed fishmeal-(100FM) or SBM-based diets supplemented with saponin (50SBM + 2SPN) from juvenile to adult stages. Individuals were selected from families with a genotype-by-environment interaction higher (HG-50SBM + 2SPN, 170 ± 18 mg) or lower (LG-50SBM + 2SPN, 76 ± 10 mg) weight gain on 50SBM + 2SPN for intestinal transcriptomic analysis. A histological evaluation confirmed middle intestinal inflammation in the LG- vs. HG-50SBM + 2SPN group. Enrichment analysis of 665 differentially expressed genes (DEGs) identified pathways associated with immunity and lipid metabolism. Genes linked to intestinal immunity were downregulated in HG fish (mpx, cxcr3.2, cftr, irg1l, itln2, sgk1, nup61l, il22), likely dampening inflammatory responses. Conversely, genes involved in retinol signaling were upregulated (rbp4, stra6, nr2f5), potentially favoring growth by suppressing insulin responses. Genes associated with lipid metabolism were upregulated, including key components of the SREBP (mbtps1, elov5l, elov6l) and cholesterol catabolism (cyp46a1), as well as the downregulation of cyp7a1. These results strongly suggest that transcriptomic changes in lipid metabolism mediate SBM tolerance. Genotypic variations in DEGs may become biomarkers for improving early selection of fish tolerant to SMB or others plant-based diets.

Chitin is an excellent material for the synthesis of nanoparticles because it is an elicitor and can form nanostructured materials. The application of chitin nanoparticles (CNPs) in plants can activate early defense responses associated with chitin. In this study, CNPs were synthesized by water in oil (W/O) emulsion using an aqueous chitin solution. The CNPs were characterized and used to evaluate the activation of genes related to early responses to chitin and the production of reactive oxygen species (ROS) on seedlings of Nicotiana benthamiana. The CNPs had an average size of 280 nm in diameter, a polydispersity of 0.299, a surface charge of 26.9 mV, and their chemical composition was corroborated by the disappearance of microaggregated CNPs treated with chitinases observed under a microscope. Seedlings treated with CNPs for one hour revealed increments in the expression of genes STZ, ATL2, and MAPK3, in contrast when they were treated with chitin oligomers, and no changes in gene CERK1 was detected in both conditions. Finally, the synthesis of ROS mediated by CNPs was detected in seedlings, which was higher than those generated by the treatment of chitin oligomers. These results demonstrated the capability to generate CNPs by emulsion, which are capable of triggering responses related to early defense in N. benthamiana more efficiently than chitin oligomers.

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.

One of the causal agents of bacterial canker is Pseudomonas amygdali pv. morsprunorum—Pam (formerly Pseudomonas syringae pv. morsprunorum). Recently detected in Chile, Pam is known to cause lesions in the aerial parts of the plant, followed by more severe symptoms such as cankers and gummosis in the later stages of the disease. This study presents the design of PCR and LAMP detection methods for the specific and sensitive identification of Pseudomonas amygdali pv. morsprunorum (Pam) from cherry trees. Twelve Pseudomonas isolates were collected, sequenced, and later characterized by Multi-locus Sequence Analysis (MLSA) and Average Nucleotide Identity by blast (ANIb). Three of them (11116B2, S1 Pam, and S2 Pam) were identified as Pseudomonas amygdali pv. morsprunorum and were used to find specific genes through RAST server, by comparing their genome with that of other Pseudomonas, including isolates from other Pam strains. The effector gene HopAU1 was selected for the design of primers to be used for both techniques, evaluating sensitivity and specificity, and the ability to detect Pam directly from plant tissues. While the PCR detection limit was 100 pg of purified bacterial DNA per reaction, the LAMP assays were able to detect up to 1 fg of purified DNA per reaction. Similar results were observed using plant tissues, LAMP being more sensitive than PCR, including when using DNA extracted from infected plant tissues. Both detection methods were tested in the presence of 30 other bacterial genera, with LAMP being more sensitive than PCR.

In recent years, the cultivated area of hazelnuts in Chile has increased significantly. Along with this rapid expansion, biotic constraints that affect the optimal development of the crop have been identified. Among these, bacterial blight disease caused by Xanthomonas arboricola pv. corylina has been particularly relevant. This pathogen has a global distribution and is present in all hazelnut-producing countries. In the spring of 2023, hazelnut orchards were sampled from the Maule to Biobío Regions of Chile. The Chilean isolates recovered from hazelnut tissues showing symptoms of bacterial blight were characterized by their ability to grow on different semi-selective media, their carbohydrate utilization profiles, hypersensitivity response in tobacco plants, and biochemical tests. Additionally, the isolates were identified based on the 16S rRNA gene and multilocus sequence analysis (MLSA) on the rpoD, gyrB, and atpD genes. The results showed that the X. arboricola pv. corylina Chilean isolates differed from previously reported isolates in other geographic areas as they are capable of metabolizing sorbitol and mannitol. Using MLSA and average nucleotide identity (ANI) comparison, these isolates were grouped into four and five phylogenetic clades, respectively, representing a significant difference from what has been reported in similar international studies.

Verticillium wilt, caused by Verticillium nonalfalfae MLST2, is an emerging disease affecting yellow-fleshed kiwifruit in Chile, and effective management strategies are currently unavailable. This study evaluated the biocontrol potential of antagonistic microorganisms against V. nonalfalfae MLST2, their interaction with different kiwifruit rootstocks, and their effects on plant physiological performance. Six Pseudomonas protegens and six Bacillus velezensis isolates were screened in vitro, and the most effective strains were subsequently evaluated with Trichoderma harzianum RGM3510 under controlled conditions. B. velezensis BcB1 and P. protegens C025 showed the highest in vitro inhibition of mycelial growth (46.2 and 40.2%, respectively). However, disease suppression in planta depended strongly on the rootstock genotype. Among the evaluated rootstocks, Z5Z6 consistently exhibited the lowest wilt severity, whereas P. protegens C025 significantly reduced disease development compared with the inoculated control. In contrast, B. velezensis BcB1 failed to suppress disease and, in some rootstocks, increased wilt severity. Although cumulative disease severity in Bruno plants was not significantly reduced by the biological treatments, P. protegens C025 produced disease levels comparable to the non-inoculated control. Moreover, treatments containing P. protegens improved stomatal conductance and photochemical reflectance index, indicating lower physiological stress associated with pathogen infection. These results demonstrate that the success of biological control against V. nonalfalfae MLST2 is determined by the interaction between antagonistic microorganisms and rootstock genotype, highlighting P. protegens C025 in combination with the Z5Z6 rootstock as a promising strategy for the integrated management of Verticillium wilt in kiwifruit.