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Pearl dilution - Equigerminal

Pearl dilution

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DNA test
The DNA test is designed to verify the presence of the pearl allele (Prl), a coat color dilution modifier discovered in horses of Iberian origin. This variant produces dilutions of the base color, introducing golden tones to the coat.


Sample requirements 

  • 20 to 30 hair roots, or
  • 5 mL of blood in a K3 EDTA tube.


    Turnaround time

    The results are available within 2 to 5 working days.

    Why test?

    Purpose of the Test

    Pearl is a rare variant that dilutes the base coat colors in a less pronounced manner than the cream variant (Cr). It can complement the effect of the Cream variant, leading to very diluted coats similar to Cream double dilutes when both are present in heterozygosity.

    Testing is crucial for breeding purposes, as heterozygous Pearl horses can produce diluted offspring when bred with another Pearl carrier or a Cream dilute horse. The impact of the Pearl dilution varies based on the horse's base color, affecting the phenotype differently across different base colors.


     Interpretation of Results for the Pearl Locus

    •  N/N - Negative for Pearl

    The horse is genetically negative for the pearl allele, meaning it does not have any copies of this genetic variant. Its phenotype reflects the natural, unaltered base coat color. This horse will not pass the pearl dilution trait to its offspring, ensuring the continuation of the base coat color in the lineage.

    • N/Prl Positive Heterozygous 

    The horse is positive for the Pearl allele in a heterozygous state, indicating it carries one copy of the pearl variant. This configuration subtly dilutes the base coat color, infusing it with golden tones, although in some instances, the dilution effect may not be visually apparent.  As a heterozygous carrier, there's a 50% probability that it will transmit this dilution trait to its offspring, potentially leading to varied coat colors among the progeny.

    • Prl/Prl -  Positive Homozygous 

    The horse is positive for the pearl allele in a homozygous state, carrying two copies of this genetic variant. This genotype manifests in a more noticeable dilution of the coat color, even in the absence of other dilution genes. Being homozygous, the horse will invariably pass the pearl allele to all of its offspring, ensuring the trait's propagation and contributing to the diversity of coat colors in future generations.
    Additional insights

    The interplay between the Cream and Pearl genes subtly yet significantly affects horse coat colors, particularly evident in horses heterozygous for both genes (N/Cr + N/Prl). These horses often resemble double cream dilutes but can be distinguished by slightly darker eye colors and a marginally darker coat. Unlike double cream dilutes, the combined dilution effect of heterozygous Cream and Pearl genes might not be as pronounced, requiring careful observation or genetic testing for accurate identification.

    Homozygous Pearl horses (Prl/Prl) exhibit a more noticeable dilution, displaying pronounced golden tones in their coats compared to their homozygous Cream counterparts (Cr/Cr), whose phenotype is lighter. Interestingly, the eye and skin colors in foals—typically blue and pinkish, respectively—tend to darken with age, while the coat lightens.

    The subtle dilution effects of a single Pearl allele (N/Prl) often go undetected without genetic analysis, as they minimally alter the horse's appearance. However, the presence of two Pearl alleles (Prl/Prl) significantly enhances the dilution, affecting not just the coat but also the eye color, with amber or green hues depending on the base coat color.

    Identified in Iberian breeds like the Purebred Lusitano (PSL) and Purebred Spanish Horse (PRE), and speculated in the Spanish Mustang, the Pearl gene's inclusion in genetic discussions highlights its broad impact across equine breeds. This genetic diversity, particularly when Pearl intersects with Cream, underscores the complexity of equine coat colors and the value of genetic testing for breeders.