LONDON (Reuters) - Australian Casey Stoner kick-starts the defence of his MotoGP title in Qatar this weekend with a point to prove.

The 22-year-old Ducati rider dominated last season with 10 wins in 18 races to become the second youngest champion in the top category.

Only three other riders have won 10 times in a single 500cc/MotoGP season, compatriot Mick Doohan and Italians Giacomo Agostini and Valentino Rossi, but Stoner still feels his talents have yet to be fully recognised.

"It's been frustrating because everyone said my results were down to other things," he told the Times last week. "It was traction control or the tyres or the bike. It pissed me off."

The signs are Stoner is channelling his anger where he needs it, psyching up for the battle ahead and the sport's first night race on Sunday.

His Ducati team boss Livio Suppo has no doubt he will be setting the pace again.

"Casey has proved himself to be the man to beat and the level of confidence he has with the bike and tyres is fantastic," Suppo told the team's Web site (www.ducati.com).

"Compared to this time last year he has improved even more and it's a great pleasure to see his world championship success has not taken anything away from his desire to win."

NIGHT RACE

The season will start at 8 p.m. British time.

"It's going to be fun to race at night but for me it won't be a completely new experience because I already did a couple of speedway and dirt-track races at night when I was a junior back in Australia," said Stoner, who took his first MotoGP win in Qatar last year.

"It will be different but I don't think it changes the job for the rider, especially because we've already had two days of tests last week to get used to the track conditions and the lights."

Spaniard Jorge Lorenzo, the 250cc world champion who has graduated to the top category with Yamaha, looked quick in those tests but Stoner has pinpointed another Iberian rider as his main rival.

"Last year Valentino Rossi didn't finish second but third," he said. "Therefore I should fear (Dani) Pedrosa more."

Pedrosa, team mate to American former champion Nicky Hayden at Repsol Honda, won two races last season but the 22-year-old lost valuable practice time after crashing in January and breaking his right hand.

Yamaha's Rossi, who has won seven world titles and held the premier-class crown for five years to 2006, finished outside the leading two last season for the first time in any category since his rookie campaign in 1996.

He has since switched from Michelin to the same Bridgestone tyres as Stoner.

"I am definitely ready to start a new challenge," said the Italian. "Yamaha have worked very hard over the winter and our new bike is very good...I am confident we are in good shape."

CHANGING PLACES

Only six of last year's 18-strong grid have remained with their teams for 2008, the 60th season of the motorcycle world championship.

Those on the move include American John Hopkins, who has switched from Suzuki to Kawasaki with Italian Loris Capirossi taking his place after leaving Ducati.

Italian Marco Melandri has left Honda and is now with Stoner at Ducati.

Lorenzo, 20, is the youngest MotoGP rider and also the only rookie with a factory team but there are plenty of other newcomers including Italian Andrea Dovizioso and San Marino's Alex de Angelis.

Britain, without a winner in the premier class since the late Barry Sheene in 1981, have double Superbike world champion James Toseland flying the flag on a Tech3 Yamaha.

"I wanted to come to MotoGP and be competitive and I'm showing I can. Now I can't wait for the first race," he said after setting the fifth best time in testing at the Losail circuit last week.

The country's best hopes of a winner are likely to rest with 17-year-old Bradley Smith who has led two of the three pre-season tests in Spain in the 125cc class for Aprilia.

(Editing by Tony Jimenez)