Tomatoes (Solanum lycopersicum L.) are the most cultivated and important vegetable crop in the world. These plants can wilt during crop growth due to fusarium wilt (fusariosis), a disease that damages tomato vascular systems. The Fusarium isolated and analyzed in this work correspond to Fusarium oxysporum f. sp. radicis-lycopersici. The isolates were molecularly identified, and analysis was done on the in vitro effects of the nanoemulsions (previously obtained from extracts of Chilean medicinal plants of the genera Psoralea and Escallonia) to inhibit mycelial and conidial germination of the isolates. Subsequently, the nanoemulsions were evaluated under greenhouse conditions for preventive control of fusariosis in the root and crown, with high levels of disease control observed using the highest concentrations of these nanoemulsions, at 250 and 500 ppm.

Botryosphaeria dieback (BD) occurs in young and old plants. In the field, the prevalence and severity of the disease increase proportionally with the age of vineyards. Among the pathogens that cause BD, Diplodia seriata is the most prevalent species in Chile and other countries with a Mediterranean climate. To date, no information is available on the susceptibility of adult wood to infection by this pathogen since most of the pathogenicity tests have been carried out on 1- or 2-year-old shoots or detached canes. Therefore, a pathogenicity test was carried out on plants under field conditions, with inoculations in 1-year-old shoots and 2- and 10-year-old wood in grapevine cv. Cabernet Sauvignon. A pathogenicity test was carried out with two isolates of D. seriata. The results for the plants show that D. seriata was significantly more aggressive on the 10-year-old than on the one- or two-year-old tissue, where the lesions were 4.3 and 2.3 cm on average, respectively. These results were compared with the lesions obtained from two-year-old canes after the isolates were activated in grape berries. Also, the Chilean isolates of D. seriata were compared phylogenetically with those from other countries, and no major differences were found between them. Our results are consistent with the damage observed in the field, contributing to the knowledge of the epidemiology of this disease in Mediterranean climates. In the future, the effect observed in cv. Cabernet Sauvignon with D. seriata on virulence at different tissue ages should be tested for other BD-causing agents and wine varieties.

In Chile, tomato is one of the most widely cultivated vegetables, with around 5,000 ha for fresh market and 8,000 ha for processing industry. During recent years, symptoms of bacterial speck caused by Pseudomonas syringae pv. tomato, have been observed more frequently in tomato plants in different regions of Chile. This pathogen was first identified in Chile in 1987 (Latorre & Lolas, 1988) and the presence of an apparent new variant was reported in 2004 (Besoain et al. 2004). To characterize the pathogen that was affecting this crop, samples of diseased tomato plants were taken in three regions of Chile. The samples were collected in 2016 in Northern Chile in Lluta Valley from the Arica y Parinacota Region, and in Central Chile, in 2014 in Limache from Valparaíso Region and in 2015 in Pichidegua from O´Higgins Region. Affected tomato plants exhibited dark brown to black lesions surrounded by yellow halos in the leaves, and dark brown to black lesions in the stems, pedicels, and peduncles. Plants tissues were macerated, and the suspension was spread on King's B medium, resulting in fluorescent colonies visualized under 366 nm UV light. LOPAT tests results of three selected isolates from different Regions, were: levan production (+), oxidase reaction (-), potato soft rot (-), arginine dihydrolase production (-), and tobacco hypersensitivity (+) (Lelliot et al. 1966). Molecular identification was carried out by amplification and sequence analysis of housekeeping genes cts, encoding citrate synthase, gyrB, encoding DNA gyrase B, and rpoD, encoding sigma factor 70 (Hwang et al. 2005; Sarkar & Guttmann 2004) (GenBank Accessions No. OK001658-OK001666). BLAST analysis of cts and rpoD genes of the three isolates resulted in a match with a 100% identity (919 bp and 491 bp respectively) with Pseudomonas syringae pv. tomato strain B13-200 (GenBank: CP019871.1). BLAST analysis of gyrB gene of two isolates resulted in a match with a 100% identity (684 bp) and one isolate with 99.85% (683 bp) with Pseudomonas syringae pv. tomato strain B13-200. To identify the race 1, each strain was inoculated in five tomato plants cv. San Pedro, susceptible to both races of P. syringae pv. tomato, and cv. Rio Grande, resistant to race 0. The tomato plants were slightly wounded with a metal sponge and then sprayed with the bacterial suspension (108 CFU mL-1) of each isolate, including the reference strain DC3000 (race 0). Negative controls were sprayed with water. The plants inoculated with Chilean strains in both cv. San Pedro and cv. Rio Grande, showed symptoms of bacterial speck after 7 days. Plants inoculated with DC3000 strain showed symptoms only in cv. San Pedro, whereas control plants remained asymptomatic. Strains were re-isolated from symptomatic plants and identified by gene sequence analyses as Pseudomonas syryngae pv. tomato. This is the first report of Pseudomonas syryngae pv. tomato race 1 in Chile. Race 1 was previously reported in Canada (Lawton and MacNeill. 1986), in Italy (Buonaurio et al. 1996), in California (Arredondo and Davis 2000), in Portugal (Cruz et al. 2010), and in other states in the USA and countries in South America, Europe, Africa, and Australia, becoming the most commonly isolated race today (Cai et al 2011). These results will be the base for future studies of epidemiology, characterization, and virulence in order to explain the outbreak of this disease and the severity of symptoms observed.

In vineyards, Botryosphaeria dieback (BD) occurs in young and old plants. In the field, the prevalence and severity of the disease increase proportionally with the age of the vineyards. Among the pathogens that cause (BD), Diplodia seriata is the most prevalent species in Chile and other countries with a Mediterranean climate. To date, no information is available on the sus-ceptibility of adult wood to infection by this pathogen since most of the pathogenicity tests have been carried out on 1- or 2-year-old shoots or detached canes. Therefore, a pathogenicity test was carried out on plants under field conditions, with inoculations in plants, on one-year-old shoots, and 2- and 10-year-old wood in grapevine cv. Cabernet Sauvignon. A pathogenicity test was carried out with two isolates of D. seriata selected in an assay in detached canes that were 2-year-old. The results on plants showed that D. seriata was significantly more aggressive on 10-year-old than on one- or two-year-old tissue. These results were compared with the lesions ob-tained from two-year-old canes. The results of this work are consistent with the damage ob-served in the field, highlight the importance of identifying each pathogenic species that causes (BD) and contribute to the knowledge of the epidemiology of this disease in Mediterranean cli-mates.

In Chile and worldwide, walnut (Juglans regia L.) production faces significant losses due to crown and root rot caused by the phytopathogen Phytophthora cinnamomi. Currently, control methods have proven insufficient or unfavorable for the environment, increasing the need for sustainable alternatives. This research evaluates nanoemulsions based on extracts of medicinal plants endemic to Chile to control P. cinnamomi in walnut crops. The methodology included an in vitro test to determine the effective inhibitory concentrations of three nanoemulsions (N80, N90, and N100) on the mycelial growth of the phytopathogen, a test on walnut plants under controlled conditions, and two field tests using concentrations between 300 and 500 ppm. The in vitro results showed that the nanoemulsions could inhibit 90% of mycelial growth at 80 to 100 ppm concentrations. In the field, the N90 nanoemulsion at 500 ppm significantly reduced disease symptoms preventively and post-inoculation, compared with the control. This research is the first to study the use of nanoemulsions from native Chilean plants to control P. cinnamomi, showing potential to reduce the use of synthetic fungicides, contributing to safer and more ecological phytosanitary management.

In Chile, lettuce is the vegetable that has increased in cultivated area the most in recent years, reaching 8,309 ha. The Coquimbo Region contributes the most to this growth in production with 3,284 ha in 2022 (ODEPA 2023). Most lettuce is grown under open field conditions, but there is significant production in greenhouses and an increase in hydroponic production systems (INIA 2017). During April to June 2021 and 2022 in the Coquimbo Region, butterhead-type lettuce seedlings (Lactuca sativa) cv. Neil, cultivated under a hydroponic system, showed severe brown to black lesions in the leaves and midrib (Figure S1). To determine the etiology of this problem, samples of diseased plants were taken. Pieces of symptomatic tissue were macerated, and the extract was spread on nutrient agar (NA) and on King's B medium (KB) and incubated at 23°C for 48 h. The bacterial colonies observed were predominantly circular, creamy-white in color with irregular margins and fluorescent in KB medium. Isolates were gram-negative strictly aerobic. LOPAT test (Lelliot et al. 1966) results of two selected isolates were: levan production (-), oxidase reaction (+), potato soft rot (-), arginine dihydrolase production (-), and tobacco hypersensitivity (+), which corresponds to the profile of Pseudomonas cichorii. Molecular identification was performed through amplification and sequencing of the 16S rRNA (GenBank Accessions No. OR540674 to OR540675), gyrB and rpoD genes (Hwang et al. 2005; Sarkar and Guttmann 2004) (GenBank Accessions No. OR558279 to OR558282). BLAST analysis of the 16S rRNA gene of the isolates resulted in a match with a 99.86% identity with P. cichorii type strain ATCC 10857 (NR_112070.1). BLAST analysis of gyrB and rpoD resulted in a match with a 100% (630/630 bp) and >99% (546/550 bp) identity respectively, with strains of P. cichorii. Five six-month-old lettuce plants cv. Desert Storm were pricked in the midrib with a toothpick smeared with a fresh colony grown on KB medium. Seven days after inoculation, the plants showed dark brown, watery lesions, characteristic of damage caused by P. cichorii (Figure S1). Bacteria were isolated again from the inoculated plants and were identified as P. cichorii using LOPAT and molecular identification techniques. Midrib rot caused by P. cichorii was reported as an emerging disease of greenhouse-grown lettuce by Cottyn et al. (2009). In Chile, P. cichorii was previously described affecting nectarine fruits (Pinto de Torres and Carreño Ibañez 1983) and reported as a pathogen of lettuce among others horticultural crops by Servicio Agrícola y Ganadero of the Government of Chile (Acuña 2008), but this is the first report of P. cichorii affecting hydroponic lettuce plants in Chile. These results will be the basis of future studies to evaluate the origin of the infection, the potential dissemination, and the implementation of disease management to avoid the damage caused by this bacterium in hydroponic systems in this crop of growing importance in Chile.