Diversity of Culturable Bacteria from Endemic Medicinal Plants of the Highlands of the Province of Parinacota, Chile.

Endemic medicinal plants that grow at altitudes in northern Chile have been traditionally used for therapeutic applications by Aymara doctors. Several studies have analyzed the biological properties of these plants for therapeutic purposes. The aim was to characterize at molecular and biochemical levels the bacteria that live in the rhizosphere and roots from endemic medicinal plants that grow between 3681-5104 m.a.s.l. in the province of Parinacota. Thirty-nine bacteria were isolated from nine medicinal plants under our laboratory conditions. These bacteria were characterized by Gram stain, hydrolase production, plant-growth promotion, anti-fungal and antibacterial activities, and 16S rDNA sequencing. A phylogenetic study revealed the presence of three major phyla, Actinomycetota (46.2%), Bacillota (43.6%), and Pseudomonadota (10.3%). The rhizobacteria strains associated with the Aymara medicinal plant exhibited several interesting biological activities, such as hydrolytic enzymes, plant-growth-promoting traits, and antibacterial and antifungal properties, indicating their potential for developing new bio-based products for agricultural or clinical applications. These results are promising and highlight the need to point toward the search for explanations of the bio-molecular basis of the therapeutic effects of medicinal plants.

First Report of Pantoea agglomerans Causing a Leaf Blight and Bulb Rot of Onion in Chile.

Onion (Allium cepa L) is an important vegetable crop in Chile with 3.675 ha (ODEPA, www.odepa.gob.cl). Since 2017, a series of symptoms has been increasingly observed, mainly in mature bulbs which include water-soaked lesions on mature leaves and external and central cataphylls, which evolve to necrotic lesions and rot, reducing yields and affecting the postharvest life. As the season progresses over 90% incidence has been estimated in severely affected fields. Symptomatic plants were collected for disease identification in summer (February 2022) in Santa Cruz, O´Higgins, Chile, (34º41'32"S and 71º27'17"W). Isolations were done on semi-selective OEM medium (Zaid et al. 2012) and isolated colonies were transferred and maintained on King's B (KB) medium. Colonies on OEM medium were yellow slightly green in the center, circular to irregular shape, elevated, smooth margin, and mucoid texture (Tho et al. 2015). On KB medium colonies were yellow cream, slightly darker in the center, with smooth margins and circular or slightly irregular. Two isolates (CHS B3, CHS B1), obtaining in three different onion fields, were further identified by PCR amplification of partial 16S rRNA using primers 27F/1492R (Frank et al., 2008). The resulting sequencing were deposited in GenBank under accession numbers OP934962.1 and OP934961.1. A BLAST search of GenBank showed that these sequences exhibited 99,89 to 100 % nucleotides similarities with multiple Pantoea agglomerans sequences. Three isolates were used to test pathogenicity on detached cataphylls and onion plants tests in the laboratory and greenhouse, respectively. Cataphylls (n=10) were surface disinfected with 2% NaOCl for 2 min, placed in sterile Petri dishes, and injected with 50 µL (106 UFC/mL) inoculum suspension with the aid of a hypodermic syringe. Cataphylls were incubated in humid chamber at 22 + 2ºC for 14 days. Additionally, three-month-old onion plants (n=10), growing in pod, were inoculated by injecting leaves with 1 mL inoculum suspension (106 UFC/mL). Plant were incubated under greenhouse for 30 days to 28ºC. An equal number of cataphylls and onion plants, injected with sterile water, were left as controls. Water soaked lesions on inoculated cataphylls appeared five days after inoculation. While onions plants develop water soaked lesion 1- 4 days after inoculation. Blight and bulb rot were observed only on inoculated plants. Symptoms were identical to those previously observed in the field. Reisolations were accomplished for 100% of the inoculated cataphylls and leaves fulfilling Koch's postulates (Biochemical characterization and PCR amplification of partial 16S rRNA). Previously, Pectobacterium carotovorum was reported causing a similar disease in Chile (Acuña 2008). However, to our knowledge this is the first report of P. agglomerans causing onion leaf blight and bulb rot in O'Higgins Region, Chile. In agreement with other reports (De Armas et al. 2015, Tho et al. 2015), leaf blight and bulb has been a very aggressive disease in Chile. These results do not exclude the possibility that other Pantoea species (Armas et al. 2015) may be involved in the leaf blight and bulb rot of onions.

The Endophytic Pseudomonas sp. S57 for Plant-Growth Promotion and the Biocontrol of Phytopathogenic Fungi and Nematodes.

Oregano from Socoroma (Atacama Desert) is characterized by its unique organoleptic properties and distinctive flavor and it is produced using ancestral pesticide-free agricultural practices performed by the Aymara communities. The cultivation in this zone is carried out under extreme conditions where the standard production of different crops is limited by several environmental factors, including aridity, high concentration of salts, and boron among others. However, oregano plants are associated with microorganisms that mitigate biotic and abiotic stresses present in this site. In this work, the S57 strain (member of the Pseudomonas genus that is closely related to Pseudomonas lini) was isolated from roots of oregano plants, which are grown in soils with high content of non-sodium salts and aluminum. This bacterium stimulates the growth of Micro-Tom tomato plants irrigated with saline-boric water. Moreover, it controls the growth of phytopathogenic fungi Fusarium oxysporum and Botrytis cinerea and the nematode Meloidogyne incognita under saline-boric conditions. Together with the high levels of bacterial biomass (~47 g/L), these results allow the establishment of the bases for developing a potential new agricultural bioproduct useful for arid and semiarid environments where commercial biological products show erratic behavior.

Diversity of culturable bacteria isolated from ancestral crops of Arica and Parinacota Region, Atacama Desert.

Arica and Parinacota Region is located at the extreme north of the Atacama Desert, where the high levels of salts and boron, lack of rain, high UV radiation, among other conditions, make this zone an extreme environment. Despite these characteristics, in the transversal valleys, different types of crops are cultivated in this region, which are associated to beneficial microorganisms with specific traits that allow plants surviving and developing under extreme conditions. However, there is incomplete information related to these microorganisms. In this work, bacteria associated with ancestral crops were isolated from oregano, alfalfa, maize, potato, and grapevine samples from Belén, Codpa, Molinos, Poconchile and Socoroma localities, representing the first report of these microorganisms in those sites. Bacteria were identified, being γ-Proteobacteria, the most frequent class (~ 74.4%), with members of Pseudomonas genus the most common isolated genus. All bacteria were functionally characterized for plant growth-promoting activities, including siderophores and auxins production, phosphate solubilization, and nitrogen fixation, revealing an extraordinary potential from these microorganisms for agricultural applications under arid and semiarid conditions.