Virulence characterization of Puccinia graminis f. sp. avenae in Argentina

Abstract

Oat stem rust, caused by Pucciniagraminis f. sp. avenae Erikss and Henning (Pga), isa disease of considerable relevance on a global scale,recognized for its destructive capacity under favorableenvironmental conditions. The characterizationof the Pga population provides valuable insights intosize, diversity, and complexity, and allows the identificationof race-specific genes potentially usefulfor breeding. This study documents for the first timethe structure and complexity of Pga populations collectedin different sites in Argentina between 2021?2023 and compares it with a population sampled in2005. We identified 22 different races among the 70isolates collected during the period, showing a highlevel of diversity in the population. Moreover, mostof the races identified in 2021, and all the races identifiedin 2022 and 2023 were different from thosefound in 2005. We reported that current populationsare more virulent and complex, and the predominant?race 11? demonstrated virulence against all 11 differentialoat lines used in this study, emphasizing itspotential threat to oat cultivation in Argentina. Thechange in population dynamics detected here suggeststhat the use of a few genes as a basis for resistance tostem rust in the Argentinian germplasm has resultedin the continuous selection of Pga phenotypes withvirulence to these resistance genes. Additionally, ourresults demonstrated that the frequency of virulenceof Pga isolates increased on most of the resistancegenes compared to the 2005 population, and there areno genes potentially useful for breeding under Argentinianconditions. These findings underscore thepressing need to expand our search for new resistancegenes and deepen our understanding of the geneticmechanisms governing resistance to stem rust in oats.Moreover, our research highlights the dynamic natureof plant-pathogen interactions, emphasizing the evolutionof Pga populations and their interaction withPga genes.