The Scot’s four-under-par 68 at Clearwater Golf Club saw her end the opening round sitting joint-third, two shots behind Nicole Broche Larsen as the Dane took route 66 to set the pace.
Pretswell, who finished sixth in the same event 12 months ago, was out in level-par after starting at the tenth before picking up shots at the second, fifth, seventh and eighth on her inward journey.
It was an excellent start to the new Ladies European Tour season for the 26-year-old Lanark-born player as she bids to build on finishing a splendid 14th on the money-list in 2015.
“I’m happy to have the new season underway after a couple months since our last event in Dubai,” said Pretswell. “I enjoyed some time off over the winter before working hard with my coach Alan Murdoch.
“I’m really happy with my first round today as I played very solid in some tough, windy conditions this afternoon.
“My ball striking was the best it has been, which made life easier in the wind, and I was very tidy on the greens, which was good to see after some hard work on my putting over the winter.”
The former Curtis Cup player added: “I am excited to be back competing and really enjoying playing golf! New Zealand is my favourite stop on tour so it’s good to start the season here.
“I have little things that I want to keep improving and I hope that if I work on them I will see further progress.”
Kelsey MacDonald, Kylie Walker and Gemma Dryburgh all opened with 73s to sit just inside the projected cut mark, but But Heather MacRae is two below the line on 75. Sally Watson wirhdrew before teeing off due to a back injury.
Ko, bidding to win the event for a third time, mixed five birdies with two bogeys as Broche Larsen carved out a one-shot lead over Frenchwoman Justine Dreher.
Another French player, former Scottish Ladies Open champion Gwladys Nocera, is sitting alongside Pretswell.
Back on the PGA Tour after his European Tour appearance in Abu Dhabi last month, Russell Knox got off to a slow start in the AT&T Pebble Beach Pro-Am.
The 30-year-old Scot carded a one-under-par 71 at Pebble Beach, where Swede Freddie Jacobsen had the day’s best score with a 65.
American Chez Reavie leads overall after an eight-under 63 at Monterey Peninsula, while world No 1 Jordan Spieth opened with a one-under 71 at Spyglass Hills to sit five shots behind Justin Rose there.
*** Tempted by the MENA Tour schedule doubling in size this season to 22 events, Duncan Stewart has chosen Spain over South Africa this weekend.
Instead of taking up a chance to play in the Dimension Data Pro-Am on the Sunshine Tour in South Africa, the Grantown-on-Spey man is joining the hopefuls at the first MENA Tour Qualifying School at Almenara in southern Spain.
His decision was influenced by last weekend’s announcement in Dubai that the third-tier circuit was expanding its footprint in nine countries across three continents.
“I have played a few MENA Tour events in the past and they are extremely well run,” said Edinburgh-based Stewart, who is being joined in the 54-hole test starting on Saturday by three compatriots - Fraser Moore, Sam Macneil and Michael Stokes.
“The circuit is going from strength to strength and is growing every year. It now will have world ranking points and the top five securing Sunshine Rour cards is a massive boost to the Tour.”
With Darren Clarke as its patron, this year’s circuit will stahe events in Spain, South Africa, Egypt and Kuwait for then first time. “I will play the regular event in Spain in April and perhaps one in Morocco, too,” added Stewart. “They are great prep for the Challenge Tour kicking off.”
Six birdies in the last eight holes earned Cawder’s Jamie Savage a share of the halfway lead in the African Amateur Stroke-Play Championship at Leopard Creek.
The back-nine burst saw Savage sign for a five-under 66 to sit on six-under, level with home trio Kyle McLatchie, Jason Rossiter and Albert Venter as well as Englishman Jamie Bowler.
Kirkhill’s Craig Ross (73) is a shot behind the quintet while Jack McDonald (Barassie) and Connor Syme (Drumoig Golf Centre) are also still in the mix, both sitting five back after matching 70s.
Frenchman Franck Daux sealed a maiden win on the Alps Tour with victory in Ein Bay Open at Sokhna in Egypt.
An impressive closing 65, seven-under, for a a 12-under-par total gave him a three-shot triumph over Julien Foret after leapfrogging his compatriot.
In the first leg of the circuit’s three-event Egypt Swing, Scot Daniel Young had missed the cut by a shot following rounds of 73 and 75.
It was a tough opening day for the Scottish contingent in the first round of the Pro Golf Tour’s Tazegout Open in Morocco.
As Germany’s Anton Kirsten set the pace with a seven-under-par 65, Ross Cameron fared best of a four-strong tartan contingent with a 73 to sit joint-34th.
Chris Robb (74), Sam Kiloh (76) and Zander Culverwell (78) all head into the second round fighting to make the 36-hole cut.
Blairgowrie’s Tom McLevy won the scratch spoils in the Midland Alliance event at Carnoustie with a level-par 68 on the Buddon Links.
Andrew Johnston, a 12-handicapper from Cupar, claimed the handicap honours with a net 66.