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

Abstract

Since the mid‐2010s, Phytophthora infestans clones that have been dominant in Western Europe from the beginning of the 21st century, for example, EU_13_A2, EU_6_A1 and EU_1_A1, are being replaced by several other emerging clones, including EU_37_A2. The objective of this study was to determine whether the main drivers for the success of EU_37_A2 in Western Europe are associated with decreased fungicide sensitivity, increased virulence and/or aggressiveness. Axenic P. infestans cultures were sampled in the 2016 and 2017 growing seasons from potato crops in France and the United Kingdom. Amongst these, four genotypes were identified: EU_37_A2, EU_13_A2, EU_1_A1 and EU_6_A1. Although a wide range of fluazinam sensitivity was found amongst individual isolates, clonal lines EU_13_A2 and EU_37_A2 showed decreased sensitivity to fluazinam. EU_37_A2 overcame the R5 differential cultivar more often than isolates of EU_1_A1 or EU_6_A1. However, this does not explain the competitive advantage of EU_37_A2 over the virulent EU_13_A2. The fittest genotype, as measured by aggressiveness under controlled conditions, was EU_6_A1, followed by EU_37_A2, EU_13_A2 and then EU_1_A1. EU_37_A2 isolates also showed a shorter latent period than either EU_6_A1 or EU_13_A2, which could favour its long‐term persistence. Overall, the data suggest that the emergence of EU_37_A2 in Western Europe was driven by its resistance to a then‐major fungicide and shorter generation time. This conclusion is further supported by the fact that EU_37_A2 emergence was slowed by the progressive reduction in the use of fluazinam as a single active ingredient in the years following its initial detection.

Genetic Diversity and Reproduction Trends of Phytophthora infestans in Estonia: EU_41_A2 Detected without an Indication of Clonal Reproduction

“…Intensive agricultural practices, including the widespread cultivation of susceptible host varieties and the increased deployment of fungicides containing the same active ingredient, have the potential to exert selective pressure on P. infestans populations. Such practices may favor the emergence and spread of fungicide-resistant clonal lineages (e.g., EU_13_A2, EU_37_A2, EU_43_A1), thus influencing shifts in population structure and leading to disease control failures [7,[16][17][18]. The virulence and fitness advantages of newly emerged clonal lineages (e.g., EU_41_A2) could play a significant role in their rapid expansion and subsequent persistence within the genetically diverse population [6].…”

Population Dynamics of Phytophthora infestans in Egypt Reveals Clonal Dominance of 23_A1 and Displacement of 13_A2 Clonal Lineage

“…The P. infestans strain 2_A1 is a dominating A1 mating type in the east African countries Burundi, Kenya, Rwanda, Tanzania and Uganda [ 21 ]. Whereas, the population structure of P. infestans in the North African countries is mostly newly emerging A2 mating types of European origin [ 13 , 22 ]. This might be due to a high import of seed potato into this region from European countries [ 19 ].…”