Ethyl-methanesulfonate mutagenesis generated diverse isolates of Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen

Authors: LI, YUXIANG - Washington State University; WANG, MEINAN - Washington State University; See, Deven; Chen, Xianming

Submitted to: World Journal of Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2019
Publication Date: 1/28/2019
Citation: Li, Y., Wang, M., See, D.R., Chen, X. 2019. Ethyl-methanesulfonate mutagenesis generated diverse isolates of Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen. World Journal of Microbiology and Biotechnology. 35:28. https://doi.org/10.1007/S11274-019-2600-6.
DOI: https://doi.org/10.1007/S11274-019-2600-6

Interpretive Summary: The stripe rust pathogen is an obligate biotrophic fungus causing one of the most important diseases of wheat worldwide. Mutation is considered as one of the major mechanisms causing virulence changes in the pathogen population, but experimental evidence is limited. To study the effect of mutation on the pathogen variation, we developed 33 mutant isolates by treating urediniospores of race PSTv-18, avirulent to all of the 18 wheat single-gene resistance lines, with chemical ethyl methanesulfonate (EMS). These isolates were characterized through virulence testing on the 18 wheat lines and with 67 molecular markers. Most of the mutant isolates had more than one-gene change to virulence and more than one changed marker, indicating that EMS is able to cause mutations at multiple genome sites, including multiple-point mutations and extensive deletions and/or insertions. The results showed that mutation can cause substantial changes in both avirulence and genomic regions. The different frequencies of virulence among the mutant isolates suggested homozygous or heterozygous avirulence loci in the parental isolate, or relative easiness of mutation at different avirulence loci. Further characterization of the mutant isolates through genome sequencing will be carried out to determine genomic and genic changes with the potential of identifying avirulence genes.

Technical Abstract: Puccinia striiformis f. sp. tritici (Pst) is an obligate biotrophic fungal pathogen causing stripe rust, one of the most important diseases of wheat worldwide. Mutation is considered as one of the major mechanisms causing virulence changes in the pathogen population, but experimental evidence is limited. To study the effect of mutation on the pathogen variation, we developed 33 mutant isolates by treating urediniospores of Pst race PSTv-18, avirulent to all of the 18 Yr single-gene differentials, with ethyl methanesulfonate (EMS). These isolates were characterized through virulence testing on the set of 18 wheat Yr single-gene lines and with 19 simple sequence repeat (SSR) and 48 single-nucleotide polymorphism (SNP) markers. Most of the mutant isolates had more than one-gene change to virulence and more than one changed marker allele, indicating that EMS is able to cause mutations at multiple genome sites, including multiple-point mutations and extensive deletions and/or insertions. The results showed that mutation can cause substantial changes in both avirulence and genomic regions. The different frequencies of virulence among the mutant isolates suggested homozygous or heterozygous avirulence loci in the parental isolate, or relative easiness of mutation at different avirulence loci. Further characterization of the mutant isolates through genome sequencing will be carried out to determine genomic and genic changes with the potential of identifying avirulence genes.