Bruni finished half a second clear of his rivals with a dominant ride to pick up a fourth world title at Mont-Sainte-Anne Bike Park in Quebec. 

In a high-speed battle, Greg Minnaar from South Africa put in a masterful run after New Zealander Matt Walker had set the early pace but with a world title on the line, there were many crashes, slips and mechanical failures. 

Britain's Laurie Greenland suffered a rear puncture while Dean Lucas from Australia took a high-speed tumble in his quest for a podium finish.

Amaury Pierron of France pushed in the closing stages to finish ahead of three-time world champion Minnaar.

Australian Troy Brosnan then skipped through the technical section to go two seconds clear at the top of the standings before Bruni brought the house down to clinch the rainbow jersey in 4min 5.544sec.

Brosnan claimed silver in 4:06.125 with Pierron rounding out the top three in 4:08.093.

In the women's race all eyes were on Nicole and Britain's Tahnée Seagrave as they returned from injury.

United States rider Samantha Soriano set the early pace but with the running order based on world ranking, Nicole was one of the middle order riders.

She lit up the charts to take the lead by a staggering 18.8 seconds.

Seagrave made a strong effort for gold but fell 1.2 seconds behind Nicole in silver and as Eleonora Farina of Italy and Switzerland's Camille Balanche failed to make an impact at the top of the leaderboard, Nicole was assured of a World Championship medal.

Australian Tracey Hannah, dominant through the UCI World Cup series, could only muster the speed for fourth place.

Marine Cabirou of France could not challenge Nicole's time but secured a one-three French podium with a ride for bronze.

Nicole took gold in 4:53.226, with Seagrave settling for silver in 4:54.430.

Cabirou took the final step on the rostrum in 4:54.920.

The French had to settle for silver in the junior men's downhill as Antoine Vidal came up short in his bid for world glory.

In a gripping final Australia's Kye A'Hern took gold in 4:17.776, with Vidal taking second place in 4:18.920.

New Zealand's first medal of the Championships went to Tuhoto-Ariki Pene, who claimed bronze in 1:19.070.

Austrian Valentina Höll won the junior women's title in 5:01.033, with Norway's Mille Johnset finishing in second place in 5:13.961.

The bronze medal went to Anna Newkirk of the US in 5:22.263.