Use the microculture method, take a slide put a drop of agar media, like corn meal agar or malt agar even PDA, on it when the media become solid transfer Alternaia inoculum to the borders of the drop, incubate in humid chamber and check undere microscope. You should able to see the chains of conidia

You can also grow your culture on sterile cellophane films placed on the surface of Petri dish with agar medium. After your culture is ready you can carefully remove cellophane with mycelium and look through the microscope.

cellophane tape method..........apply LPCB to it

The classic method for doing this is the Riddell mount or Riddell slide method.  A description can be found at http://www.laboratorystack.com/riddell-method-slide-culture/.  You also can view the entire Riddell slide in situ for less disruption of the structures.  For Alternaria we have had good results using water agar as the fungal structures are well separated or Simmons (2007; Alternaria: an Identification Manual, CBS) recommended V8 juice agar and/or potato carrot agar as giving the best results for visualizing and recording conidia and  sporophores.

You can also try this simple adhesive tape method:

http://thunderhouse4-yuri.blogspot.sk/2012/06/adhesive-tape-preparation-for.html

http://mycology.adelaide.edu.au/Laboratory_Methods/Microscopy_Techniques_and_Stains/cellotape.html

Dear Dhanushka,

Different methods mentioned above are useful. You can try. repeated trial may be fruitful to you and you may perfectly be successful.