Disease cycle of potato late blight - MSpace at the University of ...

1.1. INTRODUCTION
CHAPTER 1
Potato (Solanum tuberosum L.) is the most important food crop from the
Solanaceae family (Friedman and McDonald 1997). According to FAO (2007), it is the
fourth most important crop after maize, wheat and rice, with an annual production of
more than 323 million tonnes. In Canada, Manitoba is the second potato producer after
Prince Edward Island, and is followed by New Brunswick, Alberta, Quebec and Ontario
(Statistics Canada 2006). Potatoes are vital to the food security of millions of people in
the developing world (FAO 2006). Potato is an important source of carbohydrates,
proteins, vitamins and antioxidants (Chauvin 2001). However, the negative difference
between actual and potential potato yields is caused principally by insufficient inputs,
low quality seeds, post-harvest losses, rural infrastructure, and biotic constraints
(Zandstra 2002). In fact, among biotic constrains, late blight is the most damaging
disease on potatoes, costing farmers $3 billion annually in lost harvest and fungicide
expenses in developed countries alone (Zandstra 2002).
Potato late blight is caused by the oomycete Phytophthora infestans (Mont.) de
Bary (Daayf et al. 2001; Kamoun 2003). The pathogen infects directly by sporangia or
through zoospores, affecting leaves, stems, and potato tubers (Goodwin et al. 1998;
Vleeshouwers et al. 2000; Judelson and Blanco 2005). Integrated management of late
blight on potatoes includes the use of healthy seed, sanitation and cull clean-up, crop
rotation, scouting, forecasting techniques, fungicide programs, storage monitoring and
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