Tennis: Venus powers past Riske but second seed Bencic toppled by Vesnina

LOS ANGELES (AFP) - Seven-time Grand Slam champion Venus Williams powered into the third round of the WTA clay-court tennis tournament at Charleston on Wednesday with a 6-4, 6-2 victory over Alison Riske.

Williams, seeded third and seeking a 50th career WTA title this week, fired 20 winners, displaying a sharp service game in a match lasting less than 90 minutes.

Things didn't go so well on the green clay of Charleston for second-seeded Swiss Belinda Bencic, beaten 6-1, 6-1 by Russian Elena Vesnina.

Bencic, the world No. 10, appeared to be struggling with the same back trouble that forced her out of her opening match in Miami.

Vesnina took full advantage, advancing in just 56 minutes.

She'll next face Lourdes Dominguez, who reached the third round when Canadian Eugenie Bouchard retired with an abdominal injury.

Spain's Dominguez was leading 6-4, 1-6, 1-0 when Bouchard decided she couldn't continue.

"It's the same one (from last year), which is why I'm concerned and why I did retire," said Bouchard, who played at last year's Wimbledon with an abdominal muscle tear and said she didn't want to repeat the mistake of making the injury worse.

Williams' win was relatively straightforward, although the 35-year-old, coming off opening match defeats at Indian Wells and Miami, said it "wasn't easy".

"I think experience definitely helped," said Williams, who won the Charleston title in 2004. "She has played good matches and won titles, so just the experience of playing those important points helped me a little more today."

Williams next faces Kazakhstan's Yulia Putintseva for a place in the quarter-finals.

Putintseva defeated 15th-seeded German Sabine Lisicki 7-5, 4-6, 6-3.

In other matches on Wednesday, seventh-seeded American Sloane Stephens beat Danka Kovinic 6-4, 6-3, but former Charleston finalists Lucie Safarova and Madison Keys both bowed out.

America Louisa Chirico sent fourth-seeded Safarova packing 6-3, 6-3, while Germany's Laura Siegemund rallied for a 6-7 (3-7), 6-4,6-4 win over eighth-seeded Keys.