The invention features a method of selecting for a grape somatic embryo or grape plant having resistance to a plant pathogen using a liquid culture medium. A latching mechanism is provided according to invention hold the balance piston immobile as described above. In embodiments, the interconnection comprises compressed elastomeric members positioned between the thrust lug of the side frame and the bearing adapter in the longitudinal direction and a low friction interface between the roof of the pedestal jaw and the top of the bearing adapter.