Titleholder Venus Williams and Wimbledon champion Petra Kvitova headed a long list of seeds blown  away on Wednesday at the Dubai Open.

Williams, unbeaten in 16 matches over six years here, and Kvitova, the champion two years ago, both failed to reach the quarter-finals, and were joined by another former winner, Agnieszka Radwanska, and a former world number one, Ana Ivanovic.

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All were ousted at an upgraded tournament with a first prize which is now nearly half a million dollars, suggesting the pool of talent capable of beating the leading players has deepened.

One of them is Lucie Safarova, a 28-year-old top 20 Czech who outplayed Williams 6-4, 6-2 and whose hard-to-read left-handed serve contrasted markedly with the 34-year-old American's delivery which appeared half paced amidst on-court temperatures reaching 40 degrees.

 Karolina Pliskova, a younger Czech, whose steep serve from a six-foot one-inch frame launches an attacking game which is flat and forceful enough to trouble anyone, overcame an often excellent Ivanovic 6-2, 4-6, 6-4.

Ivanovic didn't help her cause with two double faults near the end which scuppered her chances.  

Earlier Agnieszka Radwanska, a former titleholder, was also beaten. The fifth-seeded Pole has been suffering from a virus and looked below par for the second successive day as she lost 6-4, 6-2 to Garbine Muguruza, a 21-year-old from Barcelona who looks en route for the top 20.

 And later Flavia Pennetta, a wild card entry who saved four match points against Julie Goerges of Germany in the first round, followed it by winning 6-2, 3-6, 6-1 against the seventh-seeded Angelique Kerber, another German.