Antifungal Activity and Effect of Plant-Associated Bacteria on Phenolic Synthesis of Quercus robur L.

Abstract

Europe’s forests, particularly in Ukraine, are highly vulnerable to climate change. The maintenance and improvement of forest health are high-priority issues, and various stakeholders have shown an interest in understanding and utilizing ecological interactions between trees and their associated microorganisms. Endophyte microbes can influence the health of trees either by directly interacting with the damaging agents or modulating host responses to infection. In the framework of this work, ten morphotypes of endophytic bacteria from the tissues of unripe acorns of Quercus robur L. were isolated. Based on the results of the sequenced 16S rRNA genes, four species of endophytic bacteria were identified: Bacillus amyloliquefaciens, Bacillus subtilis, Delftia acidovorans, and Lelliottia amnigena. Determining the activity of pectolytic enzymes showed that the isolates B. subtilis and B. amyloliquefaciens could not cause maceration of plant tissues. Screening for these isolates revealed their fungistatic effect against phytopathogenic micromycetes, namely Fusarium tricinctum, Botrytis cinerea, and Sclerotinia sclerotiorum. Inoculation of B. subtilis, B. amyloliquefaciens, and their complex in oak leaves, in contrast to phytopathogenic bacteria, contributed to the complete restoration of the epidermis at the sites of damage. The phytopathogenic bacteria Pectobacterium and Pseudomonas caused a 2.0 and 2.2 times increase in polyphenol concentration in the plants, respectively, while the ratio of antioxidant activity to total phenolic content decreased. Inoculation of Bacillus amyloliquefaciens and Bacillus subtilis isolates into oak leaf tissue were accompanied by a decrease in the total pool of phenolic compounds. The ratio of antioxidant activity to total phenolic content increased. This indicates a qualitative improvement in the overall balance of the oak leaf antioxidant system induced by potential PGPB. Thus, endophytic bacteria of the genus Bacillus isolated from the internal tissues of unripe oak acorns have the ability of growth biocontrol and spread of phytopathogens, indicating their promise for use as biopesticides.

Plant-Growth-Promoting Bacteria

“…Lastly, the study carried out by Bilous et al [23] finds its context in the conservation and restoration of forest. The authors isolated ten endophytic bacteria from the tissues of unripe acorns of Quercus robur L, four of which were identified as Bacillus amyloliquefaciens, Bacillus subtilis, Delftia acidovorans, and Lelliottia amnigena.…”

Lelliottia amnigena recovered from the lung of a harbour porpoise, and comparative analyses with Lelliottia spp.

“…Lelliottia spp. have been associated with the commensal microbiota of flies and the Asian tiger mosquito [10,11], and isolated from fresh and wastewater, soil, plants, air samples and fish [6,7,[12][13][14][15][16][17][18][19]. Interest in L. amnigena is increasing as this bacterium has been associated with soft rot of economically important plant crops such as onion and potato [20].…”

“… Lelliottia spp. have been associated with the commensal microbiota of flies and the Asian tiger mosquito [10, 11], and isolated from fresh and wastewater, soil, plants, air samples and fish [6, 7, 12–19]. Interest in L.…”

Untitled

“…In particular, testing in the production conditions of certain methods and techniques of reforestation inherent in environmentally oriented Forestry is being conducted, namely: focus on the plantation or positive seed production; introduction of narrow-cutting, gradual, and selective methods of logging of the main use; use of sowing seed material (especially autumn) for the formation of artificial forest stands; conducting a forestry complex of works to improve natural renewal, considering such forest-cultural measures as seed sowing and tillage. (Kulbanska, 2021; Bilous et al, 2023). Methods of long-term storage of seeds and cultivation of high-quality seedlings of forest woody plant species are still insufficiently studied, and the characteristics given in the literature are not equivalent and incomplete.…”