Yellow Suffusion or better known as Primrose or Buttercup is a gene that is not understood quite well yet, this gene cannot be identified as sex-linked, dominant, co-dominant or recessive gene. How this gene is inherited is fairly inconsistent as visual yellow suffused Cockatiels do not always reproduce a suffused yellow phenotype in offspring. Birds carrying strains of these genes have varying degrees of yellow psittacin throughout their plumage which can be misleading in some cases as birds with liver disease can display the same amount of yellow psittacin as a healthy yellow suffused bird.
This mutation/variation does not have a specific origin and has been emerging in aviary’s around the world independent from one another, breeders have been pairing yellower strains of Cockatiels to one another to produce yellower Cockatiels in order to establish this as a mutation and not only a modified version of an existing gene.
Combining this mutation with the Whitefaced mutation as well as alleles of the Whitefaced mutation would not benefit the strain of psittacin genes as the Whitefaced gene removes psittacin and it’s alleles known as par-blue(partial-blue) reduces the psittacin, pairings to melanin altering and changing mutations would compliment yellow suffusion.