Southern blot for confirmation of correct deletion of pyr2 , pks4 and ade2 . NcoI was used for all digestions together with a 485 bp probe targeting the pyr2 promoter and FLp 1. The probe was amplified using primer pair pyr2 prom-P-fw and pyr2 prom-P-rv. An arrow indicates a very faint band for MJ-T-013. An enhanced version of the picture is provided as Additional file 2: Figure S2. The three affected loci and expected band sizes are seen underneath the Southern blot picture. Marker: BstII digested λ DNA. DRR: Direct repeat recombinant, FLa 1: Upstream ade2 flank, FLa 2: Downstream ade2 flank, FLp 1: Upstream pyr2 flank, FLp 2: Downstream pyr2 flank, FLs 1: Upstream pks4 flank, FLs 2: Downstream pks4 flank.