FIG 3.

Cross-infectivity and springboard effects of PVY mutations involved in resistance breakdown (RB) in three solanaceous species. Arrows with solid lines correspond to cross-infectivity effects, and arrows with broken lines correspond to evolutionary springboard effects of RB mutations. Mutations in boxes correspond to amino acid substitutions in PVY VPg conferring RB. Arrows point toward the second resistance gene or allele for which cross-infectivity or springboard effects are observed after fixation of the mutation involved in the breakdown of a first resistance gene. The double-headed arrow indicates that the two considered resistance genes can select the mutation (symmetrical cross-infectivity).