2010 MotoGP rookie Hector Barbera joined Ducati test riders Vittoriano Guareschi and Franco Battaini for the start of a private three-day test session at Jerez on Thursday.

A rain shower limited the effective track time and forced Barbera to lap with wet weather tyres on a Marlboro-liveried Desmosedici, indicating that the young Spaniard was trying the 2010 'big bang' style engine, rather than last season's GP9, which he had used at the previous Valencia test.

Former grand prix racer Battaini was also on a factory, Marlboro-red, machine. The Italian looks set to take over at least some of Guareschi's official test rider duties, as Guareschi makes the move into team management.

Thursday also saw former KTM 125cc star Marc Marquez make his Ajo Derbi debut, riding a plain black machine with Red Bull and Repsol branding.

Weather conditions are expected to improve for Friday and Saturday.