Understanding and Exploiting Late Blight Resistance in the Age of Effectors

Abstract

Potato (Solanum tuberosum) is the world's third-largest food crop. It severely suffers from late blight, a devastating disease caused by Phytophthora infestans. This oomycete pathogen secretes host-translocated RXLR effectors that include avirulence (AVR) proteins, which are targeted by resistance (R) proteins from wild Solanum species. Most Solanum R genes appear to have coevolved with P. infestans at its center of origin in central Mexico. Various R and Avr genes were recently cloned, and here we catalog characterized R-AVR pairs. We describe the mechanisms that P. infestans employs for evading R protein recognition and discuss partial resistance and partial virulence phenotypes in the context of our knowledge of effector diversity and activity. Genome-wide catalogs of P. infestans effectors are available, enabling effectoromics approaches that accelerate R gene cloning and specificity profiling. Engineering R genes with expanded pathogen recognition has also become possible. Importantly, monitoring effector allelic diversity in pathogen populations can assist in R gene deployment in agriculture.

NLR network mediates immunity to diverse plant pathogens

“…The extensive breeding efforts for improving disease resistance within this family have led to the identification of many NLR-type disease resistance genes from wild relatives (13,14). To date, over 20 NLR-type disease resistance genes have been identified from different solanaceous species, which confer resistance to infection by diverse and destructive pathogens and pests, including the oomycete Phytophthora infestans, tomato spotted wilt virus (TSWV), and potato cyst and root-knot nematodes (13,14). Several of these solanaceous NLR-type disease resistance genes have been deployed in agriculture through traditional breeding, cisgenesis, or transgenesis (14,15).…”

“…To date, over 20 NLR-type disease resistance genes have been identified from different solanaceous species, which confer resistance to infection by diverse and destructive pathogens and pests, including the oomycete Phytophthora infestans, tomato spotted wilt virus (TSWV), and potato cyst and root-knot nematodes (13,14). Several of these solanaceous NLR-type disease resistance genes have been deployed in agriculture through traditional breeding, cisgenesis, or transgenesis (14,15). For example, Rpi-blb2 has been introgressed into potato cultivars to confer broad-spectrum resistance to isolates of P. infestans (16).…”

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

“…A zig-zag model has been proposed to explain the recognition and evasion that occurs between the plant-pathogen recognition and interaction that limits the durability of R genes (Jones and Dangl 2006;Hein et al 2009). Both potatoes and tomatoes have major genes that confer resistance to P. infestans, namely the Rpi genes in potatoes and Ph genes in tomatoes (Black et al 1953;Oyarzun et al 1998;Vleeshouwers et al 2011). Initially, a total of 11 R genes (R1-R11) from Solanum demissum were characterized for potatoes ( Table 2).…”

“…However, virulent races of P. infestans rapidly evolved to overcome the resistance, as observed for many R genes. More than 30 R genes have been identified from wild Solanum species that confer differential resistance to various Solanum species (Vleeshouwers et al 2011; Table 2). The Ph-1-Ph3 genes from Solanum pimpenellifolium have been characterized for tomatoes (Chen et al 2008;Panthee and Chen 2010) and Ph-1, Ph-2, and Ph-3 were mapped to chromosomes 7, 10, and 9, respectively ( Table 2).…”

Best Practices for Population Genetic Analyses

“…For many reasons, population genetics is a tremendously useful discipline with a long history of application to plant pathology. For example, one can establish where the likely center of origin of a plant pathogen is located, which in turn allows harnessing of plant resistance genes (Goss et al 2014;Grünwald and Flier 2005;Stukenbrock et al 2007;Vleeshouwers and Oliver 2014;Vleeshouwers et al 2011). Plant pathogens continue to emerge and reemerge and population genetic analyses can be used to infer genetic patterns (subdivision, bottlenecks, clonality, etc.…”