The picture below shows the same Trichoderma spp. grown on PDA under the same conditions. According to what I've learned from other questions answered on ResearchGate, some Trichoderma spp. produce green pigmentation while others produce yellow pigmentation. Could the same Trichoderma spp. produce both green and yellow pigment? or do I have two different species?
@ Rosina, my answer is yes. For example, Trichoderma harzianum produces yellow pigment on the medium, it's considered as secondary metabolites of this fungus, while the green color refers to conidia color.
J. C. Tarafdar
Thank you so much, I was a bit worried that I might not have a pure fungus.
Doubtless. Pigmentation often also depends on the culture medium and other environmental factors.
This condition is common in other Fungal species for example in Fusarium species, it is recommended not to use pigmentation as an identification criteria as a species may show variation in subsequent batches.
However from my experience, unless there is a change in growth conditions e.g. PH or contamination, an axenic Trichoderma species should show consistency in pigmentation a long batches.
colony pigment is mainly due to conidial color. If it is yellow the strain lacks yA gene encoding laccase
Most Trichoderma isolates produce yellow pigment in their early growth stage and that steadily changes into fully green on the abverse within five to seven days of incubation. The yellow pigment may persist visible on the back side of the plate.
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