Examining Phenotypic Traits Contributing to the Spread in Northern European Potato Crops of EU_41_A2, a New Clonal Lineage of Phytophthora infestans

Abstract

Until recently, genotypes of Phytophthora infestans were regionally distributed in Europe, with populations in western Europe being dominated by clonal lineages and those in northern Europe being genetically diverse due to frequent sexual reproduction. However, since 2013, a new clonal lineage (EU_41_A2) has successfully established itself and expanded in the sexually recombining P. infestans populations of northern Europe. The objective of this study was to study phenotypic traits of the new clonal lineage of P. infestans, which may explain its successful establishment and expansion within sexually recombining populations. Fungicide sensitivity, aggressiveness and virulence profiles of isolates of EU_41_A2 were analyzed and compared to those of the local sexual populations from Denmark, Norway, and Estonia. None of the phenotypic data obtained from the isolates collected from Denmark, Estonia and Norway independently explained the invasive success of EU_41_A2 within sexual Nordic populations. Therefore, we hypothesize that the expansion of this new genotype could result from a combination of fitness traits and more favorable environmental conditions that have emerged due to climate change.

Investigating phenotypic traits as potential drivers of the emergence of EU_37_A2, an invasive new lineage of Phytophthora infestans in Western Europe

“…A similar fluctuation in fluazinam sensitivity was also seen in the study of EU_41_A2 and the sexually reproducing P . infestans population from northern Europe in the same years (Puidet et al, 2022). Such a change may reflect a reduction in the use of this active ingredient in the first years of EU_37_A2 expansion, and thus reduced selection pressure for the highest levels of resistance.…”

“…Leaflets were collected randomly across the field, each from a different plant. Half of each lesion was used to produce an axenic culture (Puidet et al, 2022), whereas the other half was used for simple‐sequence repeat (SSR) genotyping.…”

“…The media for isolation, experiments and storage differed amongst laboratories (V8 agar, rye B agar, pea agar or a 50/50 mixture of pea and rye B agar; Puidet et al, 2022). To avoid contamination, isolates obtained from the leaf lesions were first grown on media amended with antibiotics (10 μg/ml pimaricin, 30 μg/ml rifamycin and 150 μg/ml ampicillin).…”

“…The experiment was conducted on detached leaflets collected from 6‐ to 8‐week‐old plants of the late blight susceptible potato cv. Bintje as described by Puidet et al (2022). In brief, six fully developed cv.…”

“…According to the most recent monitoring results from the EuroBlight network (EuroBlight, 2022), the three dominating clones from the past 15 years (EU_1_A1, EU_6_A1 and EU_13_A2) are currently being replaced by several emerging clones, notably EU_41_A2, EU_36_ A2 and EU_37_A2. EU_41_A2 spreads mainly in northern Europe and is more virulent than in sexually reproducing populations (Puidet et al, 2022). EU_36_A2 was first identified in 2014 in the Netherlands and has shown a greater aggressiveness than several other major clones (EuroBlight, 2022).…”