Champion and millionaire Riboletta, who was returned to racing in May after losing her Forestry foal this year because of mare reproductive loss syndrome, has been retired from racing because of a flare-up of an ankle injury. Owned by Aaron and Marie Jones, Riboletta did not start following her return to trainer Eduardo Inda at Southern California. Six-year-old Riboletta (Roi Normand--Joy Valley, by Ghadeer) will be returned to the Taylor family's Taylor Made Farm near Nicholasville. Ky. Plans call for her to be bred to Forestry next year.On July 11 at Hollywood Park, Riboletta's 3-year-old full sister, Tamara Princess, won a 6 1/2-furlong maiden race. The filly is owned by the Joneses and trained by Inda.