Is thermal aptitude a pivotal driver in the establishment of recent Puccinia striiformis f. sp. tritici lineages in Europe?

The thermal aptitude of representative isolates from the most recent common European Pst races were characterized. To this end, two key aggressiveness components—infection efficiency (IE) and latency period (LP)—were assessed under warm and cold thermal regimes, comparing 10 Pst isolates collected from 2010 to 2020 with three “old” reference isolates. The significant differences observed suggest that this species has the potential to adapt to temperature changes, but that such adaptation probably did not drive the establishment of neither the previously dominant races ‘Warrior’ and ‘Warrior(-)’, nor the following most recent races. These races display “generalist” behavior with respect to temperature, with ‘Warrior(-)’ showing no more aggressiveness than the races replaced since the 1990s. The differences in competitive success between emerging Pst lineages are probably due to the deployment of resistance genes in wheat and the advantages of new forms of virulence emerging independently of thermal adaptability. However, variations in thermal adaptability for both aggressiveness components suggested an impact of geographic origin within the ‘Warrior’ and ‘Warrior(-)’ races, as previously reported for the “old” reference isolates. Experimental evidence of temperature adaptation differences between strains suggests an impact of geographic origin within the 'Warrior' and 'Warrior(-)' races, similar to what had been reported several years ago for French reference strains from the "North" and "South."

Meyer K, Leconte M, Vidal T, Goyeau H, Suffert F. 2024. Is thermal aptitude a pivotal driver in the establishment of recent Puccinia striiformis f. sp. tritici lineages in Europe? Journal of Plant Pathology. https://doi.org/10.1007/s42161-024-01590-7