Introduction to Fungi, Third Edition

394 HYMENOASCOMYCETES: ERYSIPHALES
Fig13.2 Blumeria graminis. (a) Two-day-old germinating conidium on wheat leaf, showing penetration point surrounded by a‘halo’
(stippled). A haustorium has developed beneath the penetration point. (b) Penetration from an established mycelium. (c) Section of
an epidermal cell showing two penetration points and two haustoria. Note the thickening of the epidermal cell beneath the
penetration point. (d) Mycelium and conidia, showing the swollen flask-shaped foot cell (‘mother cell’).
is that the conidial foot cell is swollen (Fig. 13.2d).
Thirdly, scanning electron microscopy studies by
Cook et al. (1997) have shown that the surface of
the conidium of B. graminis is distinct from that of
other Erysiphales because of the spiny wall and
the raised septum surrounded by a depressed ring
(Figs. 13.3a,b). These differences are matched by
DNA sequence data (Saenz & Taylor, 1999a).