Evolution within a given virulence phenotype (pathotype) is driven by changes in aggressiveness: a case study of French wheat leaf rust populations

Abstract

Evolution within a given virulence phenotype (pathotype) is driven by changes in aggressiveness: a case study of French wheat leaf rust populations , Peer Community Journal, 3: e39.

Can higher aggressiveness effectively compensate for a virulence deficiency in plant pathogen? A case study ofPuccinia triticina’s fitness evolution in a diversified varietal landscape

“…In this study, we highlighted a significant difference in aggressiveness between two P. triticina pathogenotypes that not only differed in their genotype but also in their virulence profile, and co-dominated in the varietal landscape during a short time period (2012-2015). This result complements the findings obtained by Fontyn et al (2023), which showed a difference in aggressiveness between ’new’ pathogenotypes and ’old’ ones, all of which had the same virulence profile, over a longer period of time (2006-2016). These two complementary approaches (see Introduction) provide a strong body of evidence attesting to the role of aggressiveness in the domination of certain isolates.…”

“…The pathotyping tests were performed in a greenhouse on eight-day-old wheat seedlings grown in a plastic box containing potting soil placed under standardized conditions as described in Fontyn et al (2023). The inoculation was performed with 10 fresh (two-week-old) spores, picked one by one with a human eyelash under a dissecting microscope, then deposited on a 3 cm-long segment of the second leaf of each seedling, maintained with double-sided tape on a rigid plate coated with aluminum foil.…”

“…Fontyn et al (2023) reported that two isolates of the same pathotype are not necessarily of identical genotype, as defined by microsatellite markers, and therefore do not necessarily belong to the same clonal lineage, while identical genotypes may differ in one or several virulences. To underline this point, the authors proposed to use the term ‘pathogenotype’ to identify isolates based on a unique pathotype × genotype association.…”

“…The first approach consisted in comparing, within each of the aforementioned dominant pathotypes 106 314 0 and 166 317 0, the ‘new’ pathogenotypes (106 314 0-G2 and 166 317 0-G2) with the ‘old’ ones (106 314 0-G1 and 166 317 0-G1, respectively), considering a large time period (2006-2016). With this strategy, Fontyn et al (2023) found that the new pathogenotypes exhibited higher levels of aggressiveness compared to the old ones. They concluded that this fitness advantage can explain the replacement of isolates by others with the same virulence combinations.…”

“…Several compatible pathotypes, other than the two aforementioned, virulent against the Lr genes carried by the most widely grown cultivars, were present in the landscape but never reached substantial frequencies. Focusing on the comparative dynamics of these two dominant pathotypes (Figure 3 in Fontyn et al, 2023) highlighted three periods: (i) until 2011, the frequency of the pathotype 106 314 0 remained higher than the frequency of 166 317 0; (ii) then, from 2012 to 2015, the two pathotypes were at similar frequencies; and (iii) from 2016, 106 314 0 strongly decreased and finally disappeared, while 166 317 0 became dominant. Considering the Lr genes present in the French varietal landscape from 2011 to 2015 (Fontyn et al, 2022), the four most frequent Lr13 , Lr37 , Lr14a and Lr10 were overcome by both pathotypes 106 314 0 and 166 317 0.…”