Regarding to amplification of TDC gene from fungi by PCR, it would be interesting to clone and sequence the amplified fragment to provide information on the level of similarity to Catharanthus TDC gene.
HPLC-UV quantification of alkaloids in complex crude extract is not straightforward due to potential comigration during the separation. Determination of the limit of detection (LOD) and limit of quantification (LOQ) requires usually a signal/noise ratio >3 for LOD and >5 for LOQ. Did you estimate the LOD and LOQ in your experimental conditions? Otherwise, detection and quantification of VBL and VCR could be improved by preliminary purification steps. In addition, I would suggest an LC-MS/MS analysis to add further evidence on the production of these remarkable compounds outside plant kingdom.