Table 1.
Concentrations used to determine the sensitivity of wild-type isolates and pyrimorph-resistant mutants of Phytophthora capsici to various fungicides.
Figure 1.
Frequency distribution of EC50 values of Phytophthora capsici for pyrimorph.
A total of 226 isolates of P. capsici were collected from 40 locations in 24 provinces of China; the locations had never been treated with pyrimorph. EC50 represents the effective concentration causing 50% inhibition of mycelial growth of P. capsici.
Table 2.
Origin and sensitivity to pyrimorph of Phytophthora capsici isolates from 40 locations in China.
Table 3.
Level and stability of pyrimorph resistance for the parental wild-type isolates and the resistant mutants of Phytophthora capsici.
Figure 2.
Mycelial growth of Phytophthora capsici isolates and mutants on PDA as affected by temperature.
(A, B, C, D) Isolates designated R3-X, R11-X, R18-X, and Dz-X are mutants of Hd3, Hd11, and Hx18, respectively, and were obtained by consecutive transfers on medium amended with pyrimorph. Values are means and standard errors. Colony diameters (minus plug diameters) were measured after 4 days of growth.
Table 4.
Fitness of pyrimorph-resistant mutants (mutant designations begin with the letter R) and the corresponding parental isolates of Phytophthora capsicia.
Figure 3.
Spearman rank correlation for cross-resistance in Phytophthora capsici between pyrimorph and other fungicides.
(A) dimethomorph; (B) flumorph; (C) mandipropamid; (D) azoxystrobin; (E) cyazofamid; (F) cymoxanil; (G) chlorothalonil; (H) etridiazole; (I) fluazinam; (J) metalaxyl; and (K) zoxamide. Data points are the logarithmic values of effective concentrations for 50% mycelial growth inhibition (log EC50) among Phytophthora capsici isolates for the indicated fungicide combinations.
Figure 4.
Structure and site of the mutation in the PcCesA3 gene associated with pyrimorph resistance.
(A) Intron/exon structure of the PcCesA3 gene. Numbers represent the size in base pairs. Point mutations in pyrimorph-resistant mutants (RF>50) and the predicted amino acid substitution in the mutant gene products are indicated. (B) Alignment of partial amino acid sequences of CesA3 in P. capsici (PcCesA3). Hd3, Hd11, Hx18, and Dz21 are wild-type isolates. R3-2, R3-3, and R11-1 are pyrimorph-resistant mutants. Mutations in pyrimorph-resistant mutants of P. capsici are indicated by asterisks.
Figure 5.
Specificity of allele-specific PCR primers for detection of Phytophthora capsici mutants with high pyrimorph resistance.
R3-2, R3-3, and R11-1 are mutants with high resistance to pyrimorph and were obtained by exposure to the fungicide on agar; isolates Hd3 and Hd11 are the corresponding parental isolates.