The top-seeded Czech Kvitova leveled Canadian Rebecca Marino 6-2, 6-2 in a brisk 54 minutes, while the third-seeded Jankovic was leading Kateryna Bondarenko 4-1 in the first set on Tuesday when the Ukrainian retired on the indoor decoturf at TipsArena Linz.
Kvitova, who captured her first career Grand Slam title at the All England Club back in July, was the runner-up here in Linz two years ago.
Meanwhile, fourth-seeded Russian Anastasia Pavlyuchenkova held off Spaniard Anabel Medina Garrigues 6-4, 2-6, 6-3, sixth-seeded German Julia Goerges got past Latvian Anastasija Sevastova 6-4, 3-6, 7-6 (9-7), and seventh-seeded Slovak Dominika Cibulkova was leading Elena Baltacha 4-6, 7-6 (7-3), 1-0 when the Brit retired on Day 1.
Additional opening-round wins came for Italian Sara Errani, British lucky- loser Anne Keothavong, Russians Ksenia Pervak and lucky-loser Evgeniya Rodina, Czech Lucie Safarova, and Romanian qualifier Sorana Cirstea. Keothavong should have her hands full with Jankovic in the round of 16.
No less than five seeds are scheduled for action here on Wednesday, including Pavlyuchenkova, No. 5 German Sabine Lisicki and No. 8 Slovak Daniela Hantuchova, who will be opposed by Croat Petra Martic in an opening-rounder. The Slovakian Hantuchova was the Linz champion back in 2007.
This year's Linz titlist will pocket $37,000.