I suggest to use method given by Hyman (1984) or Schenck and Perez (1990). Of course, most of the methods works best on sandy soils, and less well in clay and organic soils.

Wet sieving and decanting method of Gerdmann and Nicolson ,1963 may be useful for arbuscular mycorrhizal fungi spore isolation. AMF cannot be cultured or multiplied artificially under lab conditions.

HI Gan,

Before starting work, make your self through with Invam website ( https://invam.wvu.edu/methods/culture-methods )

I'm not sure what you mean by isolation from soil, but a good way to catch a mycorrhizal fungus is by planting a compatible host plant in the soil, letting it get infected, and then replanting in a good planting medium like Turface MVP that allows easy collection of spores and mycelia,

I've had good results with a type of corn called "Bodacious". Just plant the corn in soil that is inoculated with the mycorrhiza and it should infect the roots. However, molecular analysis can be very complicated and finding an expert to ID the specimen by staining (I used trypan blue) and physiology can be very hard. Most of the experts work at the University of Kentucky I believe. Hope this helps and good luck!