Epiphyllous on Portulaca oleracea. Could be another Wilsoniana/Albugo, but this seems to be the most widespread oomycete associated with this host.
Measurements
Conidia: 16–18 × 12–15 μm
Images
Slides in LPCB
1,5-8: Habit
2: Conidia
3,4: Likely oogonium and antheridium