Genetic Advance through Mass Selection for Tenderness in Sweet Corn1

Mass selection for improved tenderness was conducted in the corn ( Zea mays L.) cultivar ‘Hawaiian Super-sweet No. 9’. Two selection criteria were applied separately—a pericarp thickness measurement of mature kernels, and a bite test of immature ears on the plant. Selection was carried out at 10% intensity among 400 ears each for 3 cycles by pericarp thickness and for 4 cycles by bite test. Selection based on pericarp thickness led to a genetic advance of 9.2% per cycle (from average 73.6 to 53.3 μm), with a concomitant 2.9% increase per cycle in tenderness as evaluated by the bite test. Genetic advance following selection based on the bite test was 3.9% per cycle as evaluated by the bite test and 2.9% per cycle as evaluated by pericarp micrometry, the germinal and abgerminal sides of pericarp differed consistently, with germinal 14.5% thinner than the abgerminal, but correlated so well for all cycles that only one side is advised in a selection program. A significant correlation (r=0.98) was found between average bite-test scores and immature pericarp thickness, but correlations based on individual ears were low (r=0.24). Bite-test scores were subject to high error variability (CV =25%) as opposed to pericarp micrometry (CV=12%). Both techniques deserve recommendation for tenderness-selection programs, possibly as tandem criteria for successive cycles of selection.