Population structure of Phytophthora infestans collected from potatoes in Guatemala and Honduras

Phytophthora infestans, the causal agent of late blight, remains a major constraint to potato production worldwide. In Central America, particularly in Guatemala and Honduras, information on the pathogen's population structure is limited despite its economic importance and reliance on imported seed potatoes. This study characterized the population structure of P. infestans in potato fields in Guatemala and Honduras using microsatellite markers, mitochondrial haplotypes, and mating type analyses. Four SSR-defined groups were identified, three corresponding to the previously described clonal lineages EU13A2, NI_1, and US8A2, and one putative group designated CeA (Central America). The detection of EU13A2, a lineage first reported in Europe and subsequently in Asia, indicates its establishment in Central America. All successfully characterized isolates exhibited the Ia mitochondrial haplotype, indicating limited mitochondrial diversity despite substantial nuclear SSR variation. AMOVA revealed significant genetic differentiation between Honduras and Guatemala, accounting for 24.43% of the total SSR variation (p = 0.022). Significant linkage disequilibrium was detected within the analyzed populations. The occurrence of genetically distinct P. infestans groups across the study area highlights the importance of monitoring transboundary pathogen movement in Central America.