ROME — Top-seeded Ana Ivanovic was upset by Bulgarian qualifier Tsvetana Pironkova 6-4, 5-7, 6-2 today in the second round of the Italian Open.

Venus Williams advanced to the third round by defeating Samantha Stosur 6-4, 6-1, and Serena Williams routed Alona Bondarenko 6-2, 6-0. Defending champion Jelena Jankovic defeated Flavia Pennetta 6-1, 6-4.

Ivanovic struggled with her consistency and serving and didn't seem comfortable on the red clay at the Foro Italico. She committed 59 unforced errors to Pironkova's 26.

"I felt quite flat out there and I found it a struggle to find my rhythm and to find something inside to fight," Ivanovic said. "I really struggled with my intensity today, and that obviously caused a lot of errors."

Ivanovic became the top seed of the clay-court warmup for the French Open when top-ranked Justine Henin withdrew citing fatigue. Henin announced Wednesday she would retire.

Stosur, playing her first WTA-level tournament after a long illness layoff, broke Williams' serve in the opening game of the match.

After getting a read on Stosur's serve, Williams broke back to 4-4 in the first set, then cruised through the second.

Williams won the tournament in 1999 and was the runner-up in 1998. Her best result since was a semifinal appearance two years ago.

In first-round play, Maria Kirilenko rallied to beat 18th-seeded Nadia Petrova 3-6, 7-5, 6-4. The match began Tuesday but was stopped because of rain with Kirilenko ahead 2-1 in the third set.

The 26th-ranked Kirilenko won the first clay-court title of her career at the Estoril Open last month.

In another match that began Tuesday, Ekaterina Makarova upset 13th-seeded Nicole Vaidisova 6-4, 4-6, 6-2.

Also, ninth-seeded Patty Schnyder eliminated Ukrainian qualifier Mariya Koryttseva 3-6, 6-2, 6-3 and Flavia Pennetta ousted lucky loser Olga Savchuk 6-7 (9), 6-3, 6-1. Agnieszka Radwanska rallied past wild card Roberta Vinci 3-6, 6-2, 6-2.

Also, Marion Bartoli edged Virginie Razzano 6-4, 7-5 and Vera Zvonareva beat Iveta Benesova 7-5, 4-6, 7-5. Sara Errani upset Agnes Szavay 6-0, 6-3.

Later, second-seeded Maria Sharapova faced Dominika Cibulkova.