What are the general steps on isolating fungi from infected plants?

Answer 1

There are three things to be concerned about for isolating the fungi. You want to be able to grow the fungi. You do not want to grow bacteria, which tend to grow faster than fungi and could take over the culture, and you want to be sure that the fungi you isolate actually came from the plant.

Starting with the last item first, be sure to use aseptic technique at all times. Aseptic technique is more detailed than what a forum like this is meant for, but it is something any microbiologist needs to be very familiar with.

As for growth conditions, a very good general medium for fungi is Sabourad Dextrose Agar. Do not use broth because the high water activity would favor bacterial growth. Also include antibiotics to inhibit bacteria. Chloramphenicol is a wide spectrum antibiotic that would be helpful, and you might add ampicillin and/or tetracycline to be more rigorous.

You could also try to make your growth medium slightly acidic, let's say a pH between 5 and 6, as many fungi prefer that, however, it then would also be wise to use replicate media conditions somewhat above and below your chosen pH.

Hope that helps.