An ecstatic Maria Sakkari revelled in a breakthrough victory at the Istanbul Cup after piling further misery on the woefully out-of-form Anna Karolina Schmiedlova.

Despite being the top seed in Turkey, world number 34 Schmiedlova has endured a miserable season - winning just one match to date on the WTA Tour.

And the Slovakian's poor form continued as Greek qualifier Sakkari triumphed 6-2 6-3 on Tuesday to claim her first win over a top-50 player.

"It's the best win of my career. I am so happy," Sakkari was quoted as saying by the WTA website.

Schmiedlova won just three points on her second serve in a miserable display, which saw her lose six games in succession during the first set.

The next test for Sakkari will come from Hsieh Su-wei, who beat Karin Knapp 6-7 (3-7) 7-5 6-1.

Defending champion and third seed Lesia Tsurenko also bowed out to a qualifier, losing in straight sets to Sorana Cirstea, but Kateryna Bondarenko and Johanna Larsson came through demanding clashes against Olga Govortsova and Maryna Zanevska respectively - the latter spurning two match points.

Home favourite Cagla Buyukakcay had an easier time of things, beating Marina Melnikova 6-3 6-3, and there were also first-round wins for Tsvetana Pironkova, Reka-Luca Jani, Kristina Kucova and Anastasija Sevastova, who did not drop a game against Aleksandra Krunic.