Molecular characterization of international collections of the wheat stripe rust pathogen Puccinia striiformis f. sp. tritici reveals high diversity and intercontinental migration

Authors: SHARMA-POUDYAL, SHARMA - Washington State University; BAI, QING - Washington State University; WAN, ANMIN - Washington State University; WANG, MEINAN - Washington State University; See, Deven; Chen, Xianming

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2019
Publication Date: 3/3/2020
Citation: Sharma-Poudyal, S., Bai, Q., Wan, A., Wang, M., See, D.R., Chen, X. 2020. Molecular characterization of international collections of the wheat stripe rust pathogen Puccinia striiformis f. sp. tritici reveals high diversity and intercontinental migration. Phytopathology. 110(4):933-942. https://doi.org/10.1094/PHYTO-09-19-0355-R.
DOI: https://doi.org/10.1094/PHYTO-09-19-0355-R

Interpretive Summary: The stripe rust pathogen causes one of the most important wheat diseases worldwide. To understand the global structure and genetic variation of the fungal pathogen, a total of 283 isolates collected from 16 countries in 8 geographic regions were genotyped using 24 co-dominant simple sequence repeat markers. Heterozygosity of isolates ranged from 0 to 75% with an average of 46%. Mean heterozygosity in individual countries ranged from 34 to 59%. A total of 265 multilocus genotypes (MLGs) were detected, and they were discriminated into two genetic lineages and an admix group. Genetic lineage 1 consisted of 52% of the isolates from all countries while lineage 2 consisted of 32% of the isolates, mostly from China and Uzbekistan. The Admix group consisted of 16% of the isolates, mostly from Asian countries, indicating genetic recombination. Generally, results obtained from various analyses consistently revealed high within-country diversity and low geographic region differentiation. Identical and similar MLGs were observed between proximity countries as well as between long distant countries of different continents, suggesting introduction or migration among continents. The populations in Turkey and Nepal were found to have possible recombination. The results are helpful in understanding the genetic variation and evolution of the pathogen and useful in managing the disease at a global level.

Technical Abstract: Puccinia striiformis f. sp. tritici (Pst) causes stripe rust (yellow rust), one of the most important wheat diseases worldwide. To understand the global structure and genetic variation of the fungal pathogen, a total of 283 Pst isolates collected from 16 countries in 8 geographic regions were genotyped using 24 co-dominant simple sequence repeat (SSR) markers. Heterozygosity of isolates ranged from 0 to 75% with an average of 46%. Mean heterozygosity in individual countries ranged from 34 to 59%. A total of 265 multilocus genotypes (MLGs) were detected, and Bayesian analysis discriminated the MLGs into two genetic lineages and an admix group. Genetic lineage 1 consisted of 52% of the isolates from all countries. Genetic lineage 2 consisted of 32% of the isolates, mostly from China and Uzbekistan. The Admix group consisted of 16% of the isolates, mostly from Asian countries, indicating genetic recombination. Generally, results obtained from analyses of Bayesian statistics, principal component, cluster, minimum spanning network, discriminant analysis of principal components, analysis of molecular variance, and pairwise correlation analysis consistently revealed high within-country diversity and low geographic region differentiation. Identical and similar MLGs were observed between proximity countries as well as between long distant countries of different continents, suggesting introduction or migration among continents. The zero or close zero fixation indices detected for the populations in Turkey and Nepal indicated possible recombination. The results are helpful in understanding the genetic variation and evolution of the pathogen and useful in managing the disease at a global level.