British number one Johanna Konta was knocked out of the Volvo Car Open in a shock second-round defeat by Fanny Stollar in Charleston.

Konta, 26, lost 3-6 4-6 to the 19-year-old Hungarian qualifier and world number 219.

World number 22 Konta, who had a bye in the first round, had beaten Stollar in in the Fed Cup in February, but performed well below her best.

Stollar goes on to play Kiki Bertens, the Dutch number 12 seed.

“She is really tough to play against so I was coming here expecting nothing, I was just going to play my game and focus on every point,” Stollar said.

“In the second set and in the first set as well I really just tried to keep my serve, break hers, and keep her behind the baseline.”

Earlier on Wednesday, second seed Petra Kvitova also fell to a surprise defeat. She was knocked out by fellow Czech Kristyna Pliskova, losing 6-1, 1-6, 3-6 to the world number 77.

Pliskova will next play Russian Elena Vesnina, who beat American Taylor Townsend 6-4 6-1.

Meanwhile, German fifth seed Julia Gorges beat Kristie Ahn of the United States 2-6 6-4 7-6 to set up a match with Japan’s Naomi Osaka, who won her first WTA title with victory at Indian Wells in March.