Evaluation of Antimicrobial Properties of Lichen Substances against Plant Pathogens

Abstract

Plant pathogens pose major threats on agriculture and horticulture, causing significant economic loss worldwide. Due to the continuous and excessive use of synthetic pesticides, emergence of pesticide resistant pathogens has become more frequent. Thus, there is a growing needs for environmentally-friendly and selective antimicrobial agents with a novel mode of action, which may be used in combination with conventional pesticides to delay development of pesticide resistance. In this study, we evaluated the potentials of lichen substances as novel biopesticides against eight bacterial and twelve fungal plant pathogens that have historically caused significant phytopathological problems in South Korea. Eight lichen substances of diverse chemical origins were extracted from axenic culture or dried specimen, and further purified for comparative analysis of their antimicrobial properties. Usnic acid and vulpinic acid exhibited strong antibacterial activities against Clavibacter michiganensis subsp. michiganensis. In addition, usnic acid and vulpinic acid were highly effective in the growth inhibition of fungal pathogens, such as Diaporthe eres, D. actinidiae, and Sclerotinia sclerotiorum. Intriguingly, the growth of Rhizoctonia solani was specifically inhibited by lecanoric acid, indicating that lichen substances exhibit some degrees of selectivity to plant pathogens. These results suggested that lichen substance can be used as a selective biopesticide for controlling plant disease of agricultural and horticultural significance, minimizing possible emergence of pesticide resistant pathogens in fields.

Evaluation of the Abilities of Three Kinds of Copper-Based Nanoparticles to Control Kiwifruit Bacterial Canker

“…The minimum bactericidal concentration (MBC) of the three kinds of nanoparticles was 1.56 μg/mL, which was much lower than that of thiodiazole copper (MBC > 100 μg/mL, Figure S4 ). Compared with the antibiotics [ 51 ], natural compounds [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ], and synthetic compounds [ 18 , 19 , 20 , 21 , 22 , 23 ] reported in the literature, copper-based nanoparticles also have advantages in bactericidal performance. The antibacterial mechanism of copper-based nanoparticles may be related to their compositions, morphologies, and sizes [ 52 ].…”

“…Recently, many novel compounds or methods have been developed to control kiwifruit bacterial canker, including natural products [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ], synthetic organic compounds [ 3 , 18 , 19 , 20 , 21 , 22 , 23 ], copper complexes [ 24 , 25 ], sulfur [ 26 ], bacteriophages [ 27 , 28 , 29 ], and other biological control agents [ 30 , 31 ]. These methods exhibited excellent control efficacies for kiwifruit bacterial canker.…”

Ubiquitous bacterial polyketides induce cross-kingdom microbial interactions

“…Further, they also have the potential to impact the spatial partitioning of microrganisms in a microbial consortium. The induced fungal compound lecanoric acid has been found to specifically inhibit the growth of the plant-pathogenic basidiomycete Rhizoctonia solani ( 37 ). These compounds suggest a possible mechanism by which certain microorganisms are included in and excluded from a microbial consortium (Figure 4B).…”

Discovery and Development of 4-Hydroxyphenylpyruvate Dioxygenase as a Novel Crop Fungicide Target

“…17−19 Notwithstanding, the precise mechanism underpinning Usnic acid's antifungal prowess remains elusive. 17 Significantly, Usnic acid has been identified as a natural product inhibitor that selectively targets Arabidopsis thaliana 4-hydroxyphenylpyruvate dioxygenase (AtHPPD), evincing pronounced inhibitory potency, as substantiated in previous reports. 20,21 Inspired by former studies, we reasoned that the primary antifungal mechanism of Usnic acid may be associated with inhibition of HPPD given its stringent conservation across prokaryotes and eukaryotes.…”

“…Additionally, a C-terminal α helix makes the cavity show different states, which may impact on the entry of the inhibitors and thus influence the species selectivity. 34 Although Usnic acid's antimicrobial activities have been documented, [16][17][18]36 the intricate antimicrobial mechanism remains elusive. Here, our results suggested that (+)-Usnic acid displayed antifungal activities against plant pathogenic fungi [Sclerotinia sclerotiorum (Ss).…”