Wind turbine rotor comprising a hub, a plurality of blades and at least one pitch system for rotating a blade substantially along its longitudinal axis, the pitch system comprising a motor, a drive pinion, a gear arranged to mesh with the drive pinion and a pitch bearing, the pitch bearing comprising an outer bearing ring connected to the hub, an inner bearing ring connected to a blade and, between these two bearing rings, one or more rows of rolling elements which allow both bearing rings to rotate relative to each other, wherein the inner bearing ring has an inner side, and wherein a reinforcement disc is radially fixed to the inner side of the inner bearing ring.