Genetic diversity of Phytophthora infestans in the Northern Andean region

Low genetic diversity was found within this sample of P. infestans isolates from crops within several regions of Colombia and Venezuela, revealing the presence of clonal populations of the pathogen in this region. We detected low frequency heterozygotes, and their distribution patterns might be a consequence of a high migration rate among populations with poor effective gene flow. Consistent genetic differentiation exists among isolates from different regions.The results here suggest that in the Northern Andean region P. infestans is a clonal population with some within-clone variation. P. infestans populations in Venezuela reflect historic isolation that is being reinforced by a recent self-sufficiency of potato seeds. In summary, the P. infestans population is mainly shaped by migration and probably by the appearance of variants of key effectors such as Avr3a.The potato and tomato late blight pathogen, Phytophthora infestans (Mont.) de Bary [1], has a broad host range within the Solanaceae family including Solanum phureja (yellow potato), S. betaceum (tree tomato), S. quitoense (naranjilla or lulo), Physalis peruviana (cape gooseberry), and other wild species [2,3]. Since the Irish potato famine in the 19th century, this pathogen has been thoroughly studied because of its severe economic impact on agriculture, causing billion-dollar losses annually [4].Mitochondrial and nuclear DNA regions of P. infestans have been extensively used in different regions of the world to investigate its evolutionary history and population structure [5-7]. This has led to the definition of lineages on the basis of molecular data, which has allowed the monitoring of populations and resulted in the generation of important epidemiological inferences about the pathogen's migration [5,6]. Additionally, population studies of P. infestans have been conducted to elucidate the origin and diversity of isolates from cultivated species [5,8-10] and to determine if there are any differences betwee