Hi Mihaela: Its maybe a mutation,

Hmm, could be a mutation. The funny thing about it is, that this happens regarding one and the same species, when I put parts of the colony on two new PDA plates (with the same medium components), the two plates of the same fungi develop a different macroscopic properties regarding colony structure, color, aerial hyphe etc. - e.g. One fungi mycelium is pink or orange and has a lot of aerial hyphe when on the contrary the other is dark red and has no aerial hyphe.

Do you purify your colony by single spore before?

Also the PH or the media have huge effect on the colony property.

Appearence of Fusarium sp. on PDA may change due to purification method, mutation, pH of PDA (5,7 or 9; actual pH of PDA is 5.6 which is ideal for Fusarium growth), mycotoxins production. Best method to get Fusarium with almost similar apperence is that always inoculate fresh plates by taking single fungal colony from starter culture (Culture plate which you purified at very first step from stock culture or isolation source), always use PDA media of same manfacturer, mycotoxins production also has a significant effect on appearence of Fusarium after 4 or 5 day of incubation.

Thanks for your help and answers!

I will try to culture my Fusarium species on a plate medium with fresh plant material.

@ Ambrin Sarwar

How can you know that the appearance changes because of mutation?

And those the mycotoxin production have an effect on the mycotoxin producing fungi itself (I have culture plates with only on fungi on it)?

Before mutation colour of Fusarium cullture is mostly dark purple but after mutation, mostly it is a mixture of dark and light purple (Sometimes only light purple mixed with white) colour.

Mycotoxin production has effect on the mycotoxin producing fungi, as the days of incubation increase i.e. 5 to 8 days or even more, mycotoxin production increases which is clearly indicated by dark purple colour uniformly distributed throughout the culture. When we purify it through HPLC and quantify it, clear difference can be observed.

You have culture plates with only on fungi on it, its ok. You can proceed with the very first fungal plate culture means the culture which you purified or sub cultured at first step of yours work.

@Ambrin Sarwar

Thank you very much for the explanation :)