Sister act on track in Paris

Serena and Venus Williams stayed on course for a third-round meeting at the French Open with dominant first-round victories.

Defending champion Serena was drawn against close friend Alize Lim, the pair having met through coach Patrick Mouratoglou, and the American did appear nervous to start with.

Two years ago Serena lost in the first round at a grand slam for the first time against another Frenchwoman, Virginie Razzano, but an upset never looked on the cards despite the world number one's occasional waywardness.

She made 36 unforced errors and endured a lengthy final game before wrapping up a 6-2 6-1 victory on her fifth match point.

Next Serena will play either Spaniard Garbine Muguruza or fellow American Grace Min, then after that a clash against Venus beckons.

The 33-year-old had a tough draw against Swiss Belinda Bencic, virtually half her age and last year's junior champion here and at Wimbledon.

The 17-year-old, who was two months old when Venus played her first French Open, has made rapid strides in the senior game and is already ranked in the top 100.

Her career has been overseen by Melanie Molitor, the mother of Martina Hingis, who was courtside to watch the teenager.

Bencic matched Venus for virtually the whole of the first set but the veteran's extra power eventually told and she ran away with the second to win 6-4 6-1, her first victory at Roland Garros for two years.

Should the sisters play each other, it would be their earliest ever meeting outside of the round-robin Tour Championships.

Third seed Agnieszka Radwanska had the honour of being the first winner at this year's tournament with a 6-3 6-0 victory over Zhang Shuai of China.

Neither player held serve until Radwanska made it 5-3 in the opening set, but after that the Pole, a quarter-finalist for the first time last year, was untroubled.

Radwanska said: "The first match is always tricky. It was a very wet court. I think the courts are not always dry, it's raining every day, so it makes the courts much slower.

"I don't know there is really any explanation why there was seven breaks in a row, but I guess it happens sometimes. But I think when I broke at the end of the first set I was more confident, and then I started to play much better."