High levels of diversity and population structure in the potato late blight pathogen at the Mexico centre of origin

Abstract

Globally destructive crop pathogens often emerge by migrating out of their native ranges. These pathogens are often diverse at their centre of origin and may exhibit adaptive variation in the invaded range via multiple introductions from different source populations. However, source populations are generally unidentified or poorly studied compared to invasive populations. Phytophthora infestans, the causal agent of late blight, is one of the most costly pathogens of potato and tomato worldwide. Mexico is the centre of origin and diversity of P. infestans and migration events out of Mexico have enormously impacted disease dynamics in North America and Europe. The debate over the origin of the pathogen, and population studies of P. infestans in Mexico, has focused on the Toluca Valley, whereas neighbouring regions have been little studied. We examined the population structure of P. infestans across central Mexico, including samples from Michoacán, Tlaxcala and Toluca. We found high levels of diversity consistent with sexual reproduction in Michoacán and Tlaxcala and population subdivision that was strongly associated with geographic region. We determined that population structure in central Mexico has contributed to diversity in introduced populations based on relatedness of U.S. clonal lineages to Mexican isolates from different regions. Our results suggest that P. infestans exists as a metapopulation in central Mexico, and this population structure could be contributing to the repeated re-emergence of P. infestans in the United States and elsewhere.

Comparative assessment of SSR and SNP markers for inferring the population genetic structure of the common fungus Armillaria cepistipes

“…In a first step, genetic data from both marker sets were separately transformed into principal components (PCs) and the optimal number of PCs was assessed with cross-validation (Jombart et al, 2010). Thereafter, we predefined geographic groups (that is, the four subpopulations), following the approach previously applied in a population genetic study of the oomycete pathogen Phytophthora infestans (Wang et al, 2017). The DAPC then probabilistically assigned individuals to one of the four pre-defined groups.…”

Large sub-clonal variation in Phytophthora infestans from recent severe late blight epidemics in India

“…infestans has continued this rapid change over the past 40 years but variation in its reproductive biology and thus its genetic diversity is observed globally. The pathogen is heterothallic with two mating types, A1 and A2, and the presence of both types in central Mexico and in the Nordic countries of Europe and the Netherlands has led to sexual reproduction and high genetic diversity 13 , 21 , 22 . In Western Europe however, the P .…”

A polyetic modelling framework for plant disease emergence

“…Furthermore, the need for repeated introductions to achieve emergence suggested in the present modelling work is in line with empirical indications of (a) multiple introductions resulting in disease emergence (Gladieux et al ., 2015); and (b) repeated emergence of new lineages in the case of P . infestans in the recent past (Wang et al ., 2017). Such patterns highlight key features to guide future research, both in terms of modelling and experimentation, and potentially to inform policy guidelines to prevent and manage emerging diseases.…”