The 2018 and now 2020 champion started the final day of event on Friday two shots back, but shot a 3-under 69 which saw Petersen leap-frog overnight leader, Steffanie Vogel, to take the title by two shots at 7-under for the tournament.
Petersen put on a clinical display with a bogey-free round which included three birdies on the front nine.
He then held his nerve and his two-shot lead throughout the back nine to finish 3-under for the day.
Petersen now joins the illustrious club of Trainees who have won the title twice, including recent graduate, and last year’s champion, Frazer Droop.
“It’s been an amazing week,” said Petersen.
“I obviously started well in the first round, but had to grind it out during the next two days in that wind.”
“Everyone else was playing well, but I knew I could shoot a good score on the final day and hopefully give myself a chance.”
After the cut, Petersen acquired the help of caddie, fellow trainee and Murray local, Jamie Stapleton, who he credits for his lift in performance in the last two rounds.
“I couldn’t have done it without him,” Petersen said.
“He knows this course so well and he really kept my head on straight when I was getting tense towards the end there. I can’t thank him enough.”
New South Wales claimed the trifecta, with Kogarah Golf Club trainee, Mitch Gannon and Port Macquarie trainee, Tom Biron, mirroring each others’ performance for the week, both carding a 3-under 69 and finishing at 5-under.
The final player to finish under par was Cobram-Barooga first year trainee, Steffanie Vogel, who shot a 3-over 75, to finish the tournament at 3-under.
The Rich River Trainee Classic continues to be a cornerstone of the trainee playing calendar, with the 33rd year providing another successful event.