Relative expression of the <i>TubB</i> gene in <i>Phytophthora capsici</i> isolates.

a<p>Isolates were only considered resistant (R) when they were able to grow on PDA plates amended with 30 µg ml⁻¹ zoxamide.</p>b<p>The expression of the <i>PcTubB</i> gene was normalized using the <i>PcWS21</i> gene and then calibrated to the normalized <i>PcTubB</i> mRNA value of the HX-1 isolate in the absence of zoxamide. The mean and standard deviation values indicate the average relative expression between two independent biological experiments. The relative expression was determined in isolates subjected to zoxamide for 6 hours prior to mRNA isolation.</p

Carboxylesterase and Cytochrome P450 Confer Metabolic Resistance Simultaneously to Azoxystrobin and Some Other Fungicides in <i>Botrytis cinerea</i>

Plant pathogens have frequently shown multidrug resistance (MDR) in the field, often linked to efflux and sometimes metabolism of fungicides. To investigate the potential role of metabolic resistance in B. cinerea strains showing MDR, the azoxystrobin-sensitive strain B05.10 and -resistant strain Bc242 were treated with azoxystrobin. The degradation half-life of azoxystrobin in Bc242 (9.63 days) was shorter than that in B05.10 (28.88 days). Azoxystrobin acid, identified as a metabolite, exhibited significantly lower inhibition rates on colony and conidia (9.34 and 11.98%, respectively) than azoxystrobin. Bc242 exhibited higher expression levels of 34 cytochrome P450s (P450s) and 11 carboxylesterase genes (CarEs) compared to B05.10 according to RNA-seq analysis. The expression of P450 genes Bcin_02g01260 and Bcin_12g06380, along with the CarEs Bcin_12g06360 in Saccharomyces cerevisiae, resulted in reduced sensitivity to various fungicides, including azoxystrobin, kresoxim-methyl, pyraclostrobin, trifloxystrobin, iprodione, and carbendazim. Thus, the mechanism of B. cinerea MDR is linked to metabolism mediated by the CarE and P450 genes

Genetic relationships among 15 isolates of <i>Phytophthora melonis</i>.

<p>The denrogram (UPGMA) shows the relationships among the isolates of <i>P. melonis</i> based on randomly amplified polymorphic DNA (RAPD) analysis with 16 decamer primers. Scale at the bottom depicts the genetic distance.</p

Overview of the crossing strategy used to determine the segregation of zoxamide-resistance in progeny of <i>P. capsici</i>.

<p>SET, sensitivity test; MTD, mating type determination (A1/A2); OSP, oospore progeny; UV, ultraviolet treatment; AD, adaptation to zoxamide-amended media; CR, cross; SCR, self-cross; S₀, S₁, parental isolates and first generation of isolates from self-cross hybridization, respectively; F₀, F₁, F₂, parental isolates and progeny of sexual hybridization, respectively; BC, backcross.</p

Genotype segregation pattern and expected phenotype of S1, F1, F2 and BC progeny according to the one-gene and two-gene resistance models.

<p>Genotype segregation pattern and expected phenotype of S1, F1, F2 and BC progeny according to the one-gene and two-gene resistance models.</p

Structure and site of mutation in the <i>PmCesA3</i> gene associated with carboxylic acid amide (CAA) fungicide resistance.

<p>(A) Intron/exon structure of the <i>PmCesA3</i> gene. Numbers represent the size in base pairs. Point mutations in CAA-resistant mutants and the predicted amino acid substitution in the mutant gene products are indicated. (B) Alignment of partial amino acid sequences of CesA3 in <i>P. melonis</i> (PmCesA3), <i>P. infestans</i> (PiCesA3), and <i>P. viticola</i> (PvCesA3). TJ-90, TX-21, and TX-33 were wild-type isolates. D63-1 and D70-3 were dimethomorph-resistant mutants. F58-4 and F63-11 were flumorph-resistant mutants. I63-2 and I70-5 were iprovalicarb-resistant mutants. Mutations in CAA-resistant mutants of <i>P. infestans</i>, <i>P. viticola</i> and <i>P. melonis</i> are indicated by asterisks.</p

<i>Phytophthora capsici</i> isolates used in this study.

a<p>RZ4-1, RZ3-5, and RZ13-2 are zoxamide-resistant mutants generated from PCAS1 by UV-mutagenesis. XH38-10 and XH38-13 are zoxamide-resistant mutants generated from HX-1 by zoxamide adaption.</p>b<p>Isolates were only considered resistant (R) when they were able to grow on PDA plates amended with 30 µg ml⁻¹ zoxamide.</p

Frequency distributions of EC₅₀ values (the effective concentration causing 50% inhibition of mycelial growth of <i>Phytophthora melonis</i>) for flumorph, dimethomorph and iprovalicarb.

<p>In total, 80 isolates of <i>P. melonis</i> were collected from areas never exposed to carboxylic acid amide fungicides.</p

Results of the experiments conducted to induce resistance against flumorph, dimethomorph, and iprovalicarb in <i>Phytophthora melonis</i>.

a<p>SM, spontaneous mutation. UV, UV-mutagenesis.</p>b<p>Survival frequency, number of mutants/total number of zoospores used for mutant generation.</p>c<p>EC₅₀, the effective concentration for causing 50% inhibition of mycelial growth inhibition of <i>P. melonis</i>.</p>d<p>Resistance factor  =  EC₅₀ of resistant isolates at the 10^th transfer/EC₅₀ of its parent.</p

Segregation of zoxamide-resistance in the sexual progeny of different <i>Phytophthora capsici</i> isolates.

a<p>Sexual progeny were only considered resistant (R) when they were able to grow on PDA plates amended with 30 µg ml⁻¹ zoxamide.</p