ALTOONA, Iowa – M B Prize, a speedy 3-year-old filly trained by the meet’s co-leading trainer Jon Arnett, towers over her seven Iowa-bred rivals in Friday’s $60,000 Bob Bryant Stakes. M B Prize, who has improved dramatically since her juvenile season, has run two excellent races here in recent weeks. In an Iowa-bred allowance sprint April 25, she pulled away from Bob Bryant rival Colerful Bride and several of her elders for a 3 3/4-length win. In the Mamie Eisenhower, a six-furlong sprint for Iowa-bred fillies and mares May 9, she set a demanding pace and proved tough for the 5-year-old Sumting Wong to wear down when second by 1 3/4 lengths. In the six-furlong Bob Bryant, M B Prize will face her own generation, and fellow improvers such as Kera Kera and deep closer Colerful Pride will have to step up to threaten the even-money morning-line favorite. Arnett, who is 19 for 71 at this meet, with 16 of those wins by Iowa-breds, is tied atop the standings with Lynn Chleborad. Jockey Ken Tohill has ridden 13 of Arnett’s 19 winners and will stay aboard M B Prize. Bob Bryant (race 6) Key contenders Leading the Band (Last 2: Beyers 49-59) * Impressed when easily winning her maiden April 30. Trained by Tim Martin, who is 3 for 15 when Alex Canchari rides for him. Kera Kera (Last 3 Beyers: 47-68-34) * Has splashed her way to a pair of wins over sloppy tracks this season. Trainer Kelly Von Hemel and jockey Glenn Corbett have combined to win at a 24 percent clip in 2014-15. M B Prize (Last 3 Beyers: 76-72-27) * With an alert break, she should be tough to catch. Colerful Bride (Last 3 Beyers: 63-65-47) * Late-rallying filly worked sharply last Friday, breezing five furlongs in a bullet 59.80 seconds. Gray’s Lake (race 8) Friday’s co-featured, $60,000 Gray’s Lake is competitive and attracted eight 3-year-old Iowa-bred colts and geldings, headed by the Von Hemel-trained pair of Caribbean Cowboy, the top Iowa-bred juvenile of 2014, and the untested speedster Colonel Ted, an easy winner of both of his races. Caribbean Cowboy dominated Iowa-bred opposition three times last season, including a 2 1/4-length tally over Gray’s Lake rival Kid Brock in the Iowa Cradle on Aug. 2. Corbett retains the mount. Colonel Ted easily won an April 24 Iowa-bred maiden race and beat winners in a May 10 Iowa-bred allowance by 2 1/2 lengths. He looks set for his stakes debut and will be ridden again by Alex Birzer. Key contenders Caribbean Cowboy (Last 3 Beyers: 48-48-61) * Perhaps was overmatched against open company in both 2015 efforts at Oaklawn Park and here. Should do better against Iowa-breds but drew the rail, which has not suited him recently. Kid Brock (Last 3 Beyers: 60-36-55) * Returned to form when rolling past Iowa-bred allowance foes for a three-length win May 2. Will be ridden by Ramon Vazquez, who has won with 19 percent of his 2014-15 mounts for trainer Chris Richard. Colonel Ted (Last 2 Beyers: 69-73) * Undefeated Colonel John gelding possesses the field’s two best Beyer Speed Figures. Approximator (Last 2 Beyers: 62-59) * Chased Colonel Ted in his debut. Romped by six lengths over maiden opposition May 3. Canchari, 23 for 96 at this meet, rides him for the first time.