Molecular epidemiology of European wheat powdery mildew
At the height of the Covid pandemic, epidemiologists carried out mass sequencing of the circulating virus populations to track their movements and the emergence of new variants. Such molecular epidemiological studies are rarer for plant pathogens but can be equally effective in learning about their patterns of spread. Powdery mildew is a fungal disease that affects wheat and is caused by Blumeria graminis forma specialis tritici (Bgt), To better understand how it spreads, Jigisha et al. carried out molecular epidemiological studies in 2022 and 2023 on the Bgt population over 90 locations in Europe and the Mediterranean regions, which produce 1/3rd of the global wheat harvest. Whole genome sequencing (WGS) revealed as excess of rare variants in Bgt population indicating a large variance of reproductive success between populations. Furthermore, the Northern Europe regions showed greater homogeneity and evidence that wind dispersal is a key to this stable structure, whereas the Southern Europe regions showed more evidence of smaller isolated populations. Finally, the authors identified evidence of recent selection pressure at several loci, for example at the genomic region containing AvrPm17, an avirulence gene coding for an effector recognized by the wheat resistance gene Pm17. Several sequence variants of AvrPm17 were found, including one, Variant H, that entirely evaded recognition by the plant resistance gene. Thus, this study revealed the fundamental epidemiological dynamics of wheat powdery mildew and contributed to understanding the rapid breakdown of resistance in European wheat population. (Summary by Indrani Kakati @Indranik333 @indranik18.bsky.social) PLOS Bio https://doi.org/10.1371/journal.pbio.3003097 See also the accompanying Primer by @smlatorreo.bsky.social
