UPDATE 2-Tennis-Open-Holder Ivanovic blames dizziness for defeat

* Ivanovic's dreams of retaining title shattered

* Azarenka reaches her first grand slam quarter-final

* Serb says she was feeling dizzy during the match

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By Sonia Oxley

PARIS, May 31 (Reuters) - Holder Ana Ivanovic relinquished her French Open crown after suffering dizzy spells in a 6-2 6-3 defeat by Belarussian teenager Victoria Azarenka on Sunday.

The Serb, who has suffered a dip in form since winning at Roland Garros last year and has slipped from number one to eighth in the world, said she had started to feel unwell after the first point in the fourth game when she was a break down.

"I just suddenly started feeling so dizzy, and I completely lost my balance," Ivanovic told a news conference after the fourth-round defeat.

"Ever since then it was really hard. I struggled with looking up. I started feeling very dizzy, and I was struggling a little bit to find my balance."