Evolution and Management of the Irish Potato Famine Pathogen Phytophthora Infestans in Canada and the United States

Yeen Ting Hwang,Melanie Kalischuk,Ron Howard,Dirk Prüfer,Dan Johnson,Champa Wijekoon,Lawrence Kawchuk

doi:10.1007/s12230-014-9401-0

Abstract

Late blight, caused by Phytophthora infestans (Mont.) de Bary, is the most historically significant and economically destructive disease of potatoes (Solanum tuberosum L.). In addition to potato, P. infestans can also infect tomato and some other members of the Solanaceae, and this has contributed to the recent late blight epidemic in Canada and the United States. Propagation of P. infestans in Canada and the United States has been mainly through asexual reproduction and this has led to the development of several dominant clonal lineages. Various P. infestans markers have been developed that are invaluable in monitoring the evolution and movement of these P. infestans genotypes. Population diversity and disease incidence has increased through the development of systemic fungicide insensitivity and the transcontinental shipment of the pathogen on late blight infected potato tubers and tomato plantlets. Introduction of the P. infestans A2 mating type to several regions of Canada and the United States has also increased the opportunity for sexual reproduction and recombination, potentially contributing to greater P. infestans genetic diversity and pathogenicity. Advances in P. infestans molecular analysis have revealed a complex pathogen with a genome capable of evolving relatively quickly. Management of late blight will therefore require new, multifaceted strategies which include monitoring pathogen evolution and implementing sustainable production practices.

Highlights

Late blight is a common and potentially devastating disease of potatoes (Solanum tuberosum L.) caused by the fungal-like pathogen Phytophthora infestans (Mont.) de Bary
P. infestans belongs to the oomycetes, a destructive group of non-photosynthetic eukaryotes that are closely related to the brown algae and diatoms (Sogin and Silberman 1998)
In contrast to parts of Europe and Mexico where pathogen populations are genetically very diverse, the genetic structures of P. infestans in the United States and Canada remain mostly composed of clonal lineages with mating types A1 or A2 separated geographically with few opportunities for sexual reproduction (Goodwin et al 1995, 1998)

Summary

Introduction

Late blight is a common and potentially devastating disease of potatoes (Solanum tuberosum L.) caused by the fungal-like pathogen Phytophthora infestans (Mont.) de Bary. Phenotypic markers available for characterizing P. infestans isolates include mating type (A1 or A2) (Gallegly and Galindo 1958), virulence (Malcolmson and Black 1966; Malcolmson 1969; Cooke et al 2003), host preference (Kalischuk et al 2012; Danies et al 2013), and resistance or sensitivity to the fungicide metalaxyl (Dowley and O’Sullivan 1981; Fry et al 1993).

Results

Conclusion