From ISTA's Common Laboratory Seed Health Testing Methods for Detecting Fungi:

After isolating the embryos from the seed, soaking, clearing and staining is required (staining is not an option). It is difficult to see the blue-stained mycelium in the embryo, so you must rotate/flip the embryos to closely observe the scutellum. In some infected embryos, only a few hyphae are observed, while in others the whole scutellum is covered by sparse to heavy mycelium.