To date, white Thoroughbreds have generally been more noted for their beauty than their racing ability, but while white Thoroughbreds in North America have yet to come up with a major winner, a Japanese family of "white ladies" may have produced its best representative yet in Sodashi, who won the Artemis Stakes (JPN-G3) on October 31 and had previously won the Sapporo Nisai Stakes (JPN-G3). Unbeaten in three starts, Sodashi already has a sizable fan base in Japan and will undoubtedly be watched with fervent interest as she continues her racing career.
The source of white coats in Thoroughbreds is mutations to the KIT gene, which have cropped up as spontaneous changes in the offspring of nonwhite parents. In Sodashi's case, the mutation (W14) arose in her granddam Shirayukihime, a white Japanese-bred produced from the union of Sunday Silence (a dark bay or brown with modest white markings) with the Topsider mare Wave Wind (also a dark bay or brown) and is completely separate from the W2, W5, and W22 mutations that led to the best-known American groups of white or white-spotted horses.
Aside from tiny numbers, one disadvantage white Thoroughbreds have generally had in trying to come up with good racehorses is that most of them have sprung from bloodlines rather unlikely to produce notable racers of any color. Shirayukihime was an exception to that rule. Sired by the most dominant stallion in Japanese history, she came of good bloodlines on the dam's side as well. While Wave Wind never raced, her sire Topsider was a good sire son of Northern Dancer, and her dam Storm and Sunshine (by 1979 American champion sprinter Star de Naskra) won the 1986 Test Stakes (USA-G2) and Post-Deb Stakes (USA-G3) before producing 2001 Bel Air Handicap (USA-G2) winner Smile Again, listed stakes winner Halo Sunshine, and restricted stakes winner Montecito. Both the last two named horses were multiple Grade 2-placed, and Montecito is the dam of Group 3-placed Irish listed stakes winner Bunairgead.
Shirayukihime managed only one third-place finish from nine starts, but her bloodlines were nonetheless good enough to make her a decent broodmare prospect even aside from interest in perpetuating her unusual coloration. Thus, all her 11 named foals were sired by high-class racehorses. 10 of the 11 were white, and six of those white foals were winners. The best of the group was Yukichan. A daughter of 2001 Japanese champion dirt horse Kurofune (a gray), Yukichan won three races that were accounted as Group stakes by Japanese standards and listed stakes by international standards. She has produced three winners thus far, and her eldest daughter Shiroinger (a white by Harbinger) is the dam of 2020 Kokura Nisei Stakes (JPN-G3) winner Meikei Yell (a bay by Mikki Isle). Shirakayuhime is also the dam of Marshmallow (a white full sister to Yukichan), whose first foal is the white King Kamehameha colt Hayayakki, winner of the 2019 Leopard Stakes (JPN-G3).
Hayayakki may be the first white horse to win a race accounted as a Group stakes by international standards, and Sodashi is bred on the reverse cross to that colt, as she is by Kurofune out of Buchiko (white), by King Kamehameha (the champion Japanese 3-year-old male of 2004 and a two-time Japanese champion sire) out of Shirayukihime. Thus, Sodashi was bred on good racing lines regardless of color, and her successes to date are by no means a fluke.
Top Japanese horses have proven themselves well up to international standard during the last few decades, so it may be only a matter of time before Sodashi or another white member of her burgeoning family steps outside Japan to test the competition in North America or Europe. In the meantime, look for the descendants of Shirayukihime to continue gracing Japanese racing with their beauty---and more than a little talent.