A single nucleotide polymorphism (SNP) located in the DNA sequence between the psaJ and trnP genes can distinguish white spruce (Picea glauca) from black (P. mariana) and red spruce (P. rubens). The presence of the red/black spruce-specific nucleotide can be determined indirectly by the presence of an Msp I restriction site (indicated with an asterisk). Another nearby Msp I site, present in all three of the species, is used as a positive control in the digestion reaction. Therefore, white spruce exhibit 1 bright band (2 fragments of the same size) and red or black spruce exhibit 3 bands.