Medium for sporulation?

[Richard Winder]

In article <4au0ri$pmv at netnews.ntu.edu.tw>, r3603207 at cc.ntu.edu.tw (ccc) writes:
>   How to decide a medium for sporulation?
>   I am doing screening experiment with Aspergillus niger. I use PDA 
>slants to collect the spores. Recently, many strains seemed to loss
>their ability to sporulate, but their parent strains do sporulate.
>  Is it too acidic for them to sporulate? I noted that the pH of the
>slants were very low that most of the agar slants were hydrolysed
>after autoclave. I even tried to add calcium carbonate into the medium
>
>but it didn't work. What should I do to make them sporulate?  
>

One method I've used that works is to autoclave the medium for twice the normal
time (for me, 40 minutes).  I'm not sure of the reason- caramelization of 
sugars?- but it seems to work particularly well with V-8 juice agar, or 
V-8 Juice/ corn leaf decoction mixtures.  I work with weed pathogens- I find 
the technique works for a broad range of foliar fungi, contaminants, 
opportunists, etc., including Aspergillus.  I don't find PDA to be very 
suitable for maintaining sporulation.  Although pH may have some effect, I 
tend to wory about the Carbon/Nitrogen ratio of the medium, and the total 
amount, complexity, and  variety of carbohydrates used as a nutrient source.
  -RSW

  RICHARD WINDER                    Title: Research Scientist
  Canadian Forest Service           Phone: (604) 363-0773
  Victoria, B.C.                    Internet: RWINDER at A1.PFC.Forestry.CA