Population structure of Phytophthora infestans collected from potatoes in Ecuador, Colombia, Peru, Bolivia and Uruguay

Abstract

Late blight, a destructive disease affecting potatoes, is caused by the oomycete Phytophthora infestans and remains a major threat to potato production worldwide. Understanding the population structure of this pathogen is essential for effective disease management. We examined the genetic structure of South American P. infestans populations using 182 isolates: 97 from Bolivia and southern Peru, 14 from Colombia, 57 from Ecuador (1993-2022), and 14 from Uruguay. The isolates were characterized by clonal lineage, mitochondrial haplotype, and mating type using multilocus genotypes based on microsatellite (SSR) markers. In Bolivia, only the lineage/haplotype 2A1/Ia was identified, whereas Peru exhibited both 2A1/Ia and EC1/IIa, all of which were mating type A1. Puno was the sole department where both lineages were present. In historical Ecuadorian populations, we found US1/Ib and EC1/IIa (P. infestans), as well as EC2/Ic and EC3/Ia (Phytophthora andina), while recent populations showed only US1. In Colombia, EC1/IIa and a distinct clonal lineage (CO4/Ia) were identified within the present dataset. In Uruguay, 2A1/Ia was predominant. These results provide updated insights into the genetic diversity and geographic distribution of P. infestans across South America and highlight the importance of continued regional surveillance for improved late blight management.