CBS culture collection offers very nice list of media recommended for most common filamentous fungi:

http://www.cbs.knaw.nl/index.php/food-mycology/101-mycological-media-for-food-and-indoor-fungi

The medium I prefer is PDA (potato dextrose agar). It is a good medium for grow most of the phytopathogenic fungi

For the first step you can use potato dextrose agar (PDA) as a common medium for fungal isolation after sample preparation, sterilization and put on the medium in the petri dishes under laminair flow cabinet. In the final you should be incubate in the suitable temperature until your fungi grow..

Dears colleagues, thank you so much for your answers.

Microscopic fungi are best isolated using acidified media like PDA, Czapeckdox.

In case Leptographium serpens (phytopathogenic fungi), the mycelium was obtained from logs of fire-injured P. pinaster trees. Tissues containing the fungus were placed onto 2% malt extract agar (MEA) and maintained at 25 ◦C in the dark for 2 weeks (Jacobs & Wingfield, 2001).

For Guignardia check this:

http://plantbiosecuritydiagnostics.net.au/wordpress/wp-content/uploads/2014/09/NDP-13-Black-rot-on-grapevine-Guignadia-V1.1.pdf

http://pbt.padil.gov.au/index.php?q=node/193&pbtID=117