Updated

Doha, Qatar (SportsNetwork.com) - Former world No. 1 Ana Ivanovic reached the second round, while surprise Australian Open runner-up Dominika Cibulkova went by way of an opening-round upset Tuesday at the $2.44 million Qatar Open.

The ninth-seeded Serbian Ivanovic was leading Daniela Hantuchova 7-5, 1-0 when the Slovakian retired, while the 10th-seeded Cibulkova was knotted with Russian wild card Alisa Kleybanova 5-5 in the first set of their encounter when the diminutive Slovak retired on the hardcourts at Khalifa International Tennis Complex.

More upsets occurred when American Bethanie Mattek-Sands took out 15th-seeded rising Canadian and Aussie Open semifinalist Eugenie Bouchard 7-5, 6-1 and Czech Lucie Safarova overcame 16th-seeded Belgian Kirsten Flipkens 5-7, 6-4, 6-4.

Several other women posted first-round wins, including Russian Anastasia Pavlyuchenkova, Romanians Monica Niculescu and Sorana Cirstea, Belgian Yanina Wickmayer, and Estonian slugger Kaia Kanepi.

This week's top seeds are Aussie Open champion Li Na, former Wimbledon runner- up Agnieszka Radwanska and former Wimbledon champ Petra Kvitova, who will battle Venus Williams in the round of 32 on Wednesday.

Two-time champion Victoria Azarenka is not defending her titles this week.