Veronika Kudermetova became the first winner of the Charleston Open since Serena Williams to triumph without dropping a set all week.

The 23-year-old Russian crushed the hopes of Montenegrin rival Danka Kovinic in Sunday's final, landing her maiden WTA Tour title with a 6-4 6-2 victory.

It meant Kudermetova sealed a perfect tournament, winning all six of her matches without being taken to a deciding set, just as superstar and 23-time grand slam champion Williams managed in 2012.

World number 38 Kudermetova said, quoted on the WTA website: "All the matches were really tough. It's really tough matches for nerves, and the tennis part, but I'm really proud of myself that I can take the first title. I'm really happy.

"It means a lot. It shows me that I can play really well, that I can beat good players, and if I play like this and keep working, I think I can be in the top 10 or higher."

The Copa Colsanitas title went to Colombian 19-year-old Maria Camila Osorio Serrano, a former US Open junior champion who entered the tournament on a wildcard but came through the field to also grab a first senior singles title.

She sank the trophy prospects of Slovenian fifth seed Tamara Zidansek, with the world number 180 recording a 5-7 6-3 6-4 victory, describing her success as "unreal".

Ash Barty won her first match on clay since reigning supreme at the 2019 French Open as the world number one rolled into the Volvo Car Open round of 16.

Barty – who last featured in a clay-court match en route to Roland Garros glory almost two years ago amid the coronavirus pandemic – made light work of Misaki Doi 6-2 6-1.

Miami Open champion last week, top seed Barty continued where she left off at the WTA 500 event on Wednesday, closing out proceedings in just over an hour in Charleston.

"I had to use it as an opportunity to try and build some comfort," Barty said. "I think having a couple days between Miami and playing this first match was important, to have my body rest, but to also try and prepare to change surfaces. It was a very quick turnaround, but I felt great out there tonight."

Barty – who now boasts a 15-2 win-loss record in 2021 – will next face Shelby Rogers after she outlasted 13th seed Amanda Anisimova 1-6 7-5 6-4.

As for second seed Sofia Kenin, the 2020 Australian Open champion slumped to a shock 4-6 6-3 6-4 defeat against Lauren Davis midweek.

World number four Kenin – runner-up at last year's French Open – eased to the first set but fellow American Davis, ranked 79th in the world, changed tactics to fine effect.

"I was a bit uncomfortable so I just really dug deep and really started to think about how to beat her and I found that heavy deep balls were not her favourite," the 27-year-old Davis said.

"Being on clay, the ball bounces high, pushing girls back, so it's very effective."

Kenin took a medical timeout at 3-0 down in the deciding set but, despite reeling off the next three games, she was unable to see Davis off as her 2021 woes continue.

Davis now heads into another all-American clash with teenage sensation Coco Gauff – who came from 1-3 down in the third to defeat Liudmila Samsonova 4-6 6-1 6-4 in an absorbing two-hour contest.

Belinda Bencic – the fifth seed – crashed out as Paula Badosa claimed the first top-20 win of her career following a 6-2 6-7 (2-7) 6-1 success.

Badosa will face Caty McNally in the last 16 after the 19-year-old American beat Anastasija Sevastova 7-6 (7-3) 2-6 6-4.

Seventh seed Elise Mertens was another big name to depart as Alize Cornet prevailed 7-5 6-3, although 15th seed Veronika Kudermetova and 12th seed Ons Jabeur progressed in with the minimum of fuss.

Former US Open champion Sloane Stephens, meanwhile, topped eighth seed Madison Keys 6-4 6-4.

Seeds were even more vulnerable at the Copa Colsanitas in Bogata, including the top-seeded Saisai Zheng who was dispatched 6-4 6-1 by Stefanie Voegele.

Zheng's compatriot Yafan Wang, seeded eighth, went down 6-3 6-3 to Viktoriya Tomova.

Arantxa Rus and Jasmine Paolini, the third and sixth seeds respectively, lost in three to Spanish duo Nuria Parrizas Diaz and Lara Arruabarrena.

Garbine Muguruza continued her superb start to 2021 as the former world number one won a WTA Tour-leading 21st match of the season to progress at the Volvo Car Open.

Muguruza – the sixth seed in Charleston – dispatched qualifier Magdalena Frech 6-1 6-3 in her first match of the clay court season on Tuesday.

Two-time grand slam champion Muguruza has already reached three finals this year, winning once in Dubai, and took just 70 minutes to overcome Fech on her return to Charleston following an eight-year absence. 

"I'm happy that I got this win, that I fought hard, that I kept my fighting spirit through the whole match, also in the second set which was tighter than the first set," Muguruza told reporters, in quotes reported on the WTA's official website.

Joining Muguruza in the round of 16 is third seed and fellow former grand slam champion Petra Kvitova, who saw off Storm Sanders 7-6 (7-4) 6-2 in her first-ever match at the WTA Premier tournament. 

Meanwhile, two former Charleston champions will go head-to-head after Sloane Stephens – a winner in 2016 – beat lucky loser Xinyu Wang 6-2 6-4 to tee up a second-round tie with 2019 victor Madison Keys.

Shelby Rogers took advantage of being in familiar surroundings by seeing off Kristina Mladenovic, while Monterrey Open champion Leylah Fernandez also progressed at the expense of 16th seed Shuai Zhang.

As for American sensation Coco Gauff, the 14th seed beat Tsvetana Pironkova 6-3 6-0 en route to the last 32.

There was a first-round surprise at the Colsanitas Cup in Bogota, where second seed Sara Sorribes Tormo was upstaged by 2012 French Open runner-up Sara Errani 7-5 7-5.

Colombian youngster Maria Camila Osorio got the better of American Sachia Vickery 6-3 6-2, with a potential top-100 scalp of Tereza Martincova next in her sights.