Serena Williams continued where she left off at Wimbledon by cruising into the second round of the Swedish Open at the expense of qualifier Ysaline Bonaventure on Wednesday.

The all-conquering American completed a second 'Serena Slam' - holding all four grand slam titles - by beating Spanish rising star Garbine Muguruza in straight sets in the final at the All England Club on Saturday.

Just four days after winning her sixth Wimbledon title, world number one Williams had no problems adjusting to playing on clay as she coasted to a 6-2 6-1 victory over Bonaventure in only 53 minutes. 

Williams, who will go in pursuit of a first calendar Grand Slam at the US Open next month, was in action in the last of the five matches in Bastad and the top seed was in no mood to hang around as she produced another ruthless display. 

The 21-time grand slam champion broke to love in the first game of the match and then again to lead 5-2 before serving out the set, then won the first two games of the second set as 20-year-old Belgian Bonaventure was given a lesson.

Williams, winner of this tournament two years ago, secured another two breaks to wrap up the match and set up a second-round encounter with Klara Koukalova.

There was a surprise in the second round on Wednesday, as second seed Samantha Stosur was beaten 7-6 (7-5) 6-0 by Lara Arruabarrena.

Australian Stosur is 53 places above the Spaniard in the world rankings, but Arruabarrena prevailed after winning four of the five break points she earned to seal her place in the quarter-finals.

Defending champion Mona Barthel had to battle back from a set down to beat Kiki Bertens in the first round, but had no such trouble in her second match of the tournament as she thrashed Maryna Zanevska 6-0 6-0.

Fourth seed Barthel needed just 43 minutes to put the qualifier out of her misery and remain in the hunt for another title in Sweden.

Jana Cepelova beat Olga Govortsova in a three-setter to reach the last eight, while seventh seed Johanna Larsson won a first-round match against Richel Hogenkamp.