Comparison of Late Blight Resistance and Yield of Potato Varieties

Potato, the third largest global food crop after wheat and rice, suffers from the devastating late blight disease, which causes 16% loss of yield globally (Haverkort et al., 2009). Late blight, caused by the plant pathogen Phytophtora infestans (Mont.) de Bary, is one of the most devastating potato diseases worldwide. Two phenotypic expressions of host plant resistance to P. infestans have been described. The distinction between two types of resistance, qualitative (race-specific) and quantitative (field resistance), is controlled by major R genes and minor genes. Factors controlling quantitative resistance to P. infestans have been found on almost every potato chromosome, confirming the truly polygenic nature of this trait (Gebhard and Valkonen, 2001). The most sustainable strategy to protect potato plants from late blight is to breed disease resistance (R) genes into the cultivars (Hansen et al., 2005). Potato breeding is complicated because potato cultivars are highly heterozygous autotetraploid plants (2n = 4x = 4n), they suffer from acute inbreeding depression and introduced R genes are quickly deflated by P. infestans (Fry, 2008). Also, quantitative resistance is thought to result in a more durable resistance under field conditions (Solomon-Blackburn et al., 2007; Fry, 2008). Late blight resistance breeding has been pretty much unsuccessful for more than 150 years (Muller and Black, 1952), and breeding for multigenic resistance, including field resistance, remains a major challenge (Rietman, 2012).