title: Competitive Fitness of Phakopsora pachyrhizi Isolates with Mutations in the CYP51 and CYTB Genes.
abstract: Soybean rust (Phakopsora pachyrhizi) in Brazil is mainly controlled with applications of fungicides, including demethylation inhibitors (DMI) and quinone outside inhibitors (QoI). Isolates with less sensitivity to DMI and QoI have been reported, and these have been found to have mutations in the CYP51 and CYTB genes, respectively. There have been no reports of fitness costs in isolates with mutations in CYP51 and CYTB, and the aim of this work was to compare the competitive ability of isolates with lower DMI or QoI sensitivities with that of sensitive (wild-type) isolates. Urediniospores of sensitive wild-type isolates and isolates with different CYP51 or CYTB alleles were mixed and inoculated on detached soybean leaves. After 3 weeks, urediniospores were harvested and used as inoculum for the next disease cycle. Frequencies of relevant target site mutations were monitored using the pyrosequencing method over four disease cycles. Isolates with lower DMI sensitivity and different CYP51 alleles had competitive disadvantages compared with a DMI-sensitive, wild-type CYP51 isolate. In contrast, the isolate with the F129L mutation in the CYTB gene competed equally well with a QoI-sensitive, wild-type CYTB isolate under the conditions of this experiment. The CYP51 and CYTB alleles were stable in all isolates over four disease cycles when cultivated alone.
authors.affiliation: First and fourth authors: Universidade Federal do Paraná, Rua dos Funcionários 1540, 80035-050 Curitiba, Brazil; second and third authors: BASF SE, Fungicide Research, Agricultural Center Limburgerhof, D-67117, Germany.
authors.forename: Ana C
authors.identifier: 0000-0003-3418-7873
authors.initials: AC
authors.lastname: Klosowski
authors.affiliation: First and fourth authors: Universidade Federal do Paraná, Rua dos Funcionários 1540, 80035-050 Curitiba, Brazil; second and third authors: BASF SE, Fungicide Research, Agricultural Center Limburgerhof, D-67117, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Brahm
authors.affiliation: First and fourth authors: Universidade Federal do Paraná, Rua dos Funcionários 1540, 80035-050 Curitiba, Brazil; second and third authors: BASF SE, Fungicide Research, Agricultural Center Limburgerhof, D-67117, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Stammler
authors.affiliation: First and fourth authors: Universidade Federal do Paraná, Rua dos Funcionários 1540, 80035-050 Curitiba, Brazil; second and third authors: BASF SE, Fungicide Research, Agricultural Center Limburgerhof, D-67117, Germany.
authors.forename: Louise L May
authors.initials: LL
authors.lastname: De Mio
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D001938:Brazil; D000072505:Cytochrome P450 Family 51 / Q000235:genetics*; D045303:Cytochromes b / Q000235:genetics*; D025141:Drug Resistance, Fungal / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics; D005659:Fungicides, Industrial / Q000494:pharmacology; D005838:Genotype; D009154:Mutation; D000067563:Phakopsora pachyrhizi / Q000235:genetics / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013025:Glycine max / Q000382:microbiology*
chemical_list: D005656:Fungal Proteins; D005659:Fungicides, Industrial; D045303:Cytochromes b; D000072505:Cytochrome P450 Family 51
keywords: Asian soybean rust; fungicide resistance