Segregation for resistance, ipiO response and genetic markers in the F1 population Sto1705-4��RH.

(A) Resistance to P. infestans isolates 90128, USA618, IPO-C, and VK98014. Six days post inoculation (dpi), 14 progeny genotypes showed extensively sporulating lesions exceeding 15 mm (susceptible, S) whereas the remaining 19 genotypes displayed localized HR spots smaller than 5 mm at the inoculation sites (resistant, R). (B) Effector response to A. tumefaciens clones expressing pGR106-ipiO1K143N, -IpiO2, -IpiO41 (PexRD6-1, -2, -3 from Table 2 respectively) and -Crn2 (positive control) and the pGR106-empty vector (negative control) was determined by monitoring for presence (+) or absence (?) of local necrosis arond the inoculation site at 14 dpi. (C) The genetic marker CT88 which is genetically closely linked to Rpi-blb1 (0.3 cM ) is assessed for presence (+) or absence (?) of the polymorphic band.1The inconsistent response of IpiO4 in the parental clone and the F1 progeny plants illustrates the potential problems that are associated with expression of the candidate effectors from a viral genome. Expression levels are apparently amenable to subtle differences in genetic constitution of the plants being tested, underlining the need for confirmation through complementary approaches.