ABSCISIC ACID LEVELS AND GENETIC COMPACTION IN APPLE SEEDLINGS

Apple (Malus sylvestris Mill.) seedlings arising from controlled crosses involving McIntosh Wijcik segregate reliably into normal and compact growth types. The compact or spur-type seedlings have shorter, thicker stems; shorter internodes; and a strong upright, nonbranching growth habit. They contained less free ABA per shoot tip than normal seedlings. A reliable and rapid method for extracting and measuring ABA is described.