Chimeral Structure of Red Sports of ‘Northern Spy’ Apple1

Blushed-fruited sports of striped ‘Northern Spy’ apple ( Malus pumila Mill.) are thought to have a mutation for this color pattern in layers I and II of the apical meristem. 1) Increased anthocyanin occurred in the epidermis (derived from L I) and in the hypodermis and outer flesh cells (derived from L II) of mature fruits of 5 sports. 2) One sport crossed with a yellow cultivar produced more blushed- than striped-fruited progeny, indicating that gene(s) for blush were in L II. 3) Three sports consistently produced blushed fruits in the orchard or following gamma irradiation of 3000–5000 rads applied to dormant buds, suggesting that the mutation was in at least the 2 outer layers. Furrowed-fruit mutants were the result of unequal cell size and unsymmetrical growth of the flesh. In 2 of 11 such mutants, anthocyanin was not formed in the depressed area, where the outer cells degenerated.