Wanda Toscanini Horowitz, conductor Arturo Toscanini's daughter who nurtured and guarded her husband, pianist Vladimir Horowitz, through his legendary but turbulent career, has died. She was 90.

"To be the daughter of Toscanini, I didn't have any merit because I could have been born to anybody," she once said. "But to be the wife of Horowitz, in that I take a little bit of pride."Mrs. Horowitz, who was married to the Russian-born pianist for 55 years, died Friday at her Manhattan home. The cause of death was not disclosed.

She was born in Milan, Italy, the youngest of four children. As a child, she aspired to follow in her father's footsteps but gave up as a teenager when her talent fell short of her expectations.

She then went to work as an assistant to her mother, who oversaw the maestro's needs for his concert tours. It was in this capacity that she met Horowitz when he gave his first solo performance with Toscanini in 1933.

"She was intoxicated by his playing," said pianist Mordecai Shehori, a family friend.

The couple were married in Milan on Dec. 21, 1933. They briefly separated in 1949, and their daugh-ter Sonia, a troubled woman who was seriously injured in a motorcycle accident, committed suicide in 1974 at age 40.

"She never really got over it, I think. But she never talked about it," Shehori said Saturday.

When Horowitz temporarily retired from public performances in 1953, Mrs. Horowitz sold her collection of impressionist paintings to put food on the table.

"I went with him through very difficult times. For 12 years he was not playing, and I kept silent," she said shortly before his death on Nov. 5, 1989. "I never prompted him, pushed him to play."

Horowitz was praised as perhaps the greatest pianist of all time, though no recordings exist of the legendary 19th century virtuoso Franz Liszt.

Mrs. Horowitz served as her husband's business confidant, shielding him from "groupies" and making sure he had the comforts of home on the road, Shehori said.