Assessment of the Sensitivity of Some Plant Pathogenic Fungi to 6-Demethylmevinolin, a Putative Natural Sensitizer Able to Help Overcoming the Fungicide Resistance of Plant Pathogens

Abstract

Agricultural fungicides contaminate the environment and promote the spread of fungicide-resistant strains of pathogenic fungi. The enhancement of pathogen sensitivity to these pesticides using chemosensitizers allows the reducing of fungicide dosages without a decrease in their efficiency. Using Petri plate and microplate bioassays, 6-demethylmevinolin (6-DMM), a putative sensitizer of a microbial origin, was shown to affect both colony growth and conidial germination of Alternaria solani, A. alternata, Parastagonospora nodorum, Rhizoctonia solani, and four Fusarium species (F. avenaceum, F. culmorum, F. oxysporum, F. graminearum) forming a wheat root rot complex together with B. sorokiniana. Non- or marginally toxic 6-DMM concentrations suitable for sensitizing effect were determined by the probit analysis. The range of determined concentrations confirmed a possibility of using 6-DMM as a putative sensitizer for the whole complex of root rot agents, other cereal pathogens (A. alternata, P.nodorum), and some potato (R. solani, A. solani) and tomato (A. solani) pathogens. Despite the different sensitivities of the eight tested pathogens, 6-DMM lacked specificity to fungi and possessed a mild antimycotic activity that is typical of other known pathogen-sensitizing agents. The pilot evaluation of the 6-DMM sensitizing first confirmed a principal possibility of using it for the sensitization of B. sorokiniana and R. solani to triazole- and strobilurin-based fungicides, respectively.

Antifungal Activity of the Dry Biomass of Penicillium chrysogenum F-24-28 and Is Application in Combination with Azoxystrobin for Efficient Crop Protection

“…Fusarium fungi attract attention of numerous researchers [25,33]. Representatives of this genus included in this study (F. oxysporum, F. graminearum, F. culmorum and F. avenaceum) are very common pathogens infecting wheat, rye, barley, oats and many other crops [15].…”

“…Enhancement of the pathogen sensitivity to fungicides by various nontoxic substances, or chemosensitization, is now one of the promising directions of studies in the field of crop protection. The effect of a combined application of a fungicide and a sensitizer can be either additive, or synergistic [10,33]. The obtained mutant P. chrysogenum F-24-28 strain demonstrated a high antagonistic activity to some plant pathogenic fungi.…”

“…A high stability of PAF and PAFB within a wide range of pH and temperature made them suitable for therapeutic use in medicine, as well as crop and food protection. Another compound, 6-demethylmevinolin (6-DMM) produced by P. citrinum was found to influence on both colony growth and conidial germination of A. solani, A. alternata, P. nodorum and R. solani, as well as four Fusarium fungi (F. avenaceum, F. culmorum, F. oxysporum and F. graminearum) forming together with Bipolaris sorokiniana a complex of root rots of wheat [33]. Like triazoles, 6-DMM inhibits the biosynthesis of sterols forming fungal cell walls; however, unlike DMI fungicides, its target is 3-hydroxy-3-methylglutaryl CoA-reductase, which is involved in the early stages of the sterol biosynthesis.…”

A Secondary Metabolite Secreted by Penicillium citrinum Is Able to Enhance Parastagonospora nodorum Sensitivity to Tebuconazole and Azoxystrobin

“…In Vitro Evaluation of 6-DMM Sensitizing Effect Towards P. nodorum Resistant to Tebuconazole Methods for sensitization experiments involving checkerboard assays and multifold double-dilution tests were previously reported (Canton et al, 2005;Orhan et al, 2005;Campbell et al, 2012). The Limpell method (Richer, 1987) used for the determination of the synergistic effect involving 6-DMM/ fungicide combinations has also been reported previously (Shcherbakova et al, 2020a). Briefly, 6-DMM sensitizing activity towards the tebuconazole-resistant strain (m8-4) was evaluated by cultivation on PDA containing Folicur ® at sub-fungicidal concentrations combined with 6-DMM at non-fungicidal or marginally fungicidal doses.…”

“…To select sub-fungicidal concentrations suppressing growth of a non-resistant pathogen by less than 50%, preliminary experiments were carried out. The range of 6-DMM concentrations presumably suitable for sensitization of P. nodorum were calculated previously (Shcherbakova et al, 2020a). In addition, minimal inhibitory concentrations (MICs) of 6-DMM, Folicur ® , and Quadris ® preventing a visible colony growth of wild M-4 and B-8/47 strains as well as 6-DMM MICs for the two most resistant mutants (m8-4 and kd-18), and MICs of Folicur ® and Quadris ® for m8-4 and kd-18, respectively, were determined according to Espinel-Ingro et al (2012) (Supplementary Table 1).…”