Genetic structure, virulence and fungicide sensitivity of Pyrenophora teres f. teres and P. teres f. maculata populations from western Canada

• Author / Creator

  Akhavan, Alireza

• The fungi Pyrenophora teres f. teres (Ptt) and P. teres f. maculata (Ptm) cause net form net blotch (NFNB) and spot form net blotch (SFNB) of barley, respectively. The genetic structure of a collection of 128 Ptt and 92 Ptm isolates, representing fungal populations from western Canada, was studied by simple sequence repeat (SSR) marker analysis. Thirteen SSR loci were examined and found to be polymorphic within both Ptt and Ptm populations. Significant genetic differentiation (PhiPT = 0.230, P = 0.001) was found among all populations. Isolates clustered in two distinct groups conforming to Ptt or Ptm, with no intermediate cluster. PCR analysis with mating type (MAT)-specific primers indicated that the MAT1 and MAT2 idiomorphs of Ptt and Ptm could be identified within the same field and on the same plants. There was no significant departure from the expected 1:1 MAT1/MAT2 ratio for either form. The virulence of a subset of 39 Ptt and 27 Ptm isolates was tested by inoculating these isolates onto barley differential hosts. Cluster analysis revealed 16 and 13 pathotype groups, respectively, among the Ptt and Ptm isolates. The barley differentials CI 5791 and CI 9820 were resistant to all Ptt isolates except one, while the differential CI 9214 was resistant to all Ptm except two. These differentials may prove useful in resistance breeding efforts, especially since some isolates were found to be highly virulent on barley cultivars previously classified as having good or very good NFNB and/or SFNB resistance. The propiconazole and pyraclostrobin sensitivity of a subset of 39 Ptt and 27 Ptm isolates also was evaluated against discriminatory doses of 5 mg propiconazole L-1 and 0.15 mg pyraclostrobin L-1 in microtiter plate bioassays. Two Ptt isolates appeared to be insensitive to propiconazole (growth inhibition < 30%), while one Ptm isolate was insensitive to pyraclostrobin and also exhibited decreased sensitivity to propiconazole. Populations of Ptt and Ptm from western Canada appear to be genetically and pathogenically diverse, and farmers should avoid planting the same resistant barley cultivars in short rotation, as well as the excessive application of the same fungicidal modes of action.

• Subjects / Keywords

  • Barley
  • Net blotch
  • Virulence
  • Western Canada
  • Genetic structure
  • Resistance
  • Pyrenophora teres
  • Fungicide sensitivity

• Graduation date

  Spring 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3X921X0M

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.