Periderm reinforcement in tubers from TA-habituated somaclone RB9.

a) Number of phellem cell layers from parent cultivar Russet Burbank tubers (RBP; white bars) compared to RB9 tubers (grey bars) according to tuber size where size 1 = 0.8 to 1.2 cm; size 2 = 1.3 to 1.7 cm; size 3 = 2.2 to 2.6 cm; and size 4 = 2.7–3.2 cm. Values represent the average number of cell layers calculated from 4 different tubers ± SEM. Means labelled by * were significantly different (P = 0.031) using Welch’s t-test. b) and c) Micrographs of autofluorescent phellem cells in tubers from RBP (b) and RB9 (c). Bar = 100 μm.