Quantitative RT-PCR revealed peaks of expression for the selected effector candidates during plant infection. A. Schematic representation of the stages of PST development during plant infection. B. Quantitative RT-PCR was undertaken at four stages of PST-08/21 infection for a subset of 22 effector candidates. Three peaks of expression were noted at 1 day post-inoculation (dpi), 6 dpi and 14 dpi. hpi, hours post-inoculation; S, uredinospore; SV, substomatal vesicle; IH, invasive hyphae; HM, haustorial mother cell; H, haustorium; P, pustule; G, guard cell.