A new coat color termed “Russet” has been identified in Burmese cats with Australian and New Zealand lineages.The russet phenotype develops with age. Young russet kittens have color and markings largely identical to tabby kittens of the same age and base color, regardless of whether the kitten is agouti (A-) or non-agouti (aa) in genotype. However, the tail-tip, genital area, and fur around the paw pads are pale in russets rather than marked with dense eumelanin as in tabbies. The nose leather is entirely pink rather than outlined in eumelanin, and the paw pads are pale, later losing all melanin to become bright pink. As the kitten grows, the solid eumelanin areas are progressively overlain with presumably phaeomelanin (red pigment), starting at the head, which usually turns entirely red. On the dorsal surfaces, broad tipping of the fur with pheaomelanin develops gradually. There is also some reduction in density of melanin in the bottom half of the hair nearest the skin. The mature cat is superficially reddish all over, but with the eumelanin pigment in the dorsal undercoat visible to an extent that varies between individuals. The mutation responsible for Russet color was identified by Dr. Leslie Lyons and her research group at the University of Missouri. Russet is an autosomal recessive trait which means that two copies of the russet allele are needed to produce the phenotype.
The VGL has developed a genetic test for Russet in Burmese and related breeds. Cats of questionable coloration, including those considered to be Dilute Modifier, should test for russet prior to considering the cat as having Dilute Modifier.
Results reported as:
N/N: No copies of the Russet mutation
N/R: 1 copy of the Russet mutation
R/R: 2 copies of the Russet mutation. Cat is or will turn Russet in color when mature
N. A. Gustafson, B. Gandolfi and L. A. Lyons. Not another type of potato: MC1R and the russet coloration of Burmese cats. Animal Genetics 2016, DOI: 10.1111/age.12505.