Histopathology of Seed-Borne Infections - Applied Research Center ...

112 Histopathology of Seed-Borne InfectionsACBDFIGURE 5.5 Mycelium of Sclerospora graminicola in pearl millet seed. A to C, Clearedwhole-mount prepartions of pericarp, endosperm and scutellum, respectively, showing themycelium. D, Mycelium from seed tissues showing constrictions and forked haustoria (arrow).(From Shetty, H.S. et al. 1978. Seed Sci. Technol. 6: 935–941. With permission.)(Figure 5.6A). The latter can be subclassified into (1) seeds partly covered withwhite crust, (2) bold-discolored with white mycelium and oospores, and (3) shriveleddiscolored seeds. The symptomatic seeds are usually smaller and lighter than thesymptomless seeds. Coenocytic, branched, and intercellular mycelium of A. candidaoccurs in seed epidermis, hypodermis, and rarely, superficial layers of cotyledonsin symptomatic seeds (Figures 5.6B to D). Fungal mycelium was observed in about4% of symptomless seeds from seed lots of infected crop plants. Symptomatic seedscarried the mycelium in seed coat together with sex organs (oogonia and antheridia)and immature to mature oospores (Figure 5.6E to G). Occasionally the myceliumalso invaded the endosperm and embryo. Embryonal infection took place only rarelyin heavily infected seeds belonging to the last two categories (Sharma, Agarwal, and