Gene RB confers enhanced tuber late blight disease resistance . Field grown tubers of nontransformed ‘Russet Burbank’ (WT) and SP2211 (+RB), a transformed ‘Russet Burbank’ line carrying the RB transgene, were mechanically wounded, inoculated with Phytophthora infestans, and incubated for 11 days under conditions that favor disease development. Tubers were peeled to allow assessment of diseased tissues. WT tubers consistently show robust tuber late blight disease development, revealed as darkened tissue radiating from inoculation sites. In contrast, +RB tubers displayed no tuber late blight disease. Note that brown spots present on +RB tubers are in response to mechanical wounding, not late blight disease; similar wound response was observed in water-inoculated tubers (not shown).