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.

Fungal diseases, both pre- and post-harvest, are currently difficult to control—increased antifungal resistances have further stimulated the search for natural alternatives. The objective of the present research work was to evaluate the antifungal activities of Mentha pulegium essential oil (EO) and its major constituents. The EO was obtained from hydro distillation of fresh leaves, and composition was determined using gas chromatography/mass spectrometry (GC/MS). The main components were identified as pulegone (29.33%), menthol (28.79%), menthone (20.48%), and isopulegol (9.75%). EO and isopulegol exhibited the highest antifungal activity, with half maximal effective concentrations (EC₅₀) inhibiting mycelial activity of Monilinia fructicola at 24.6 µg/mL and 20.8 µg/mL, respectively, and against Botrytis cinerea, at 301.45 µg/mL and 333.84 µg/mL, respectively. These findings could lay the foundation for developing antifungal agents of agricultural value.

9. Trunk diseases in grapevine (Vitis vinifera) have been identified as a major problem in the wine and table grape industries around the world, reducing the productivity, quality and longevity of vineyards. The present study examined 694 wood samples from the cordons and trunks of vines with trunk disease symptoms in 67 Chilean vineyards located between Copiapó (27°18’ S) and Los Angeles (37°42’ S). A total of 1,363 fungal isolates were obtained from diseased cordons and trunks with dark brown streaking, yellowish softspongy cankers and brown hard V-shaped cankers. Using molecular identification, a total of 12 fungal genera were identified in Chile at varying frequencies: Phaeomoniella chlamydospora (85%); Botryosphaeriaceae (56%) including Diplodia mutila, D. seriata, Neofusicoccum parvum and Spencermartinsia viticola; Inocutis sp. (47%); Diatrypaceae (Cryptovalsa ampelina and Eutypella leprosa) (4.8%); Seimatosporium botan (1.7%); Phomopsis viticola (0.4%); Cylindrocarpon sp. (0.4%); and Phaeoacremonium aleophilum (0.2%). All species were pathogenic, inducing dark brown streaking on various aged grapevine wood tissue. In conclusion, several fungal species are associated with grapevine trunk diseases in the Chilean vineyards being Pa. chlamydospora, D. seriata and Inocutis sp. the most frequent isolated species. These are pathogens that can be found alone or they can coexist in the same plant. This is the first report of Pho. viticola associated with trunk diseases in Chile

Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 µg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 µg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens.

Several Botryosphaeriaceae species have been identified as the causes of cankers and dieback of Vitis vinifera in several grape-growing regions around the world. This research was conducted to further study the species of Botryosphaeriaceae associated with table grapes in Chile, to estimate the prevalence and severity of the disease as a function of vineyard age, to study the susceptibility of table grape cultivars to infection by Botryosphaeriaceae species, and to evaluate the effect of tissue age on the infection caused by Botryosphaeriaceae species. Symptoms were characterized by the presence of the partial or total death of the grapevine cordons and distorted leaves. Brown V-shaped or U-shaped cankers and black spots were observed in cross-sections, while brown vascular streaks were observed in longitudinal sections of the cordons and trunks. Pathogenic isolates of Diplodia seriata, D. mutila and Spencermartinsia viticola were consistently obtained from wood cankers and/or vascular streaking; D. seriata was the most common (83.3%) Botryosphaeriaceae species. In 11- to 20-year-old vineyards, the disease incidence varied between 22.0 and 69.0%, and the severity varied between 6.0 and 21.3%. The table grape cultivars ‘Thompson Seedless’, ‘Redglobe’ and ‘Flame Seedless’ were equally susceptible to infection by D. mutila, D. seriata and S. viticola. The age of the inoculated tissue had no significant effect on the development of the vascular necrosis. This is the first report of D. mutila and S. viticola infections of grapevines in Chile.