Pericarp thickness in maize (Zea mays L.) was analyzed by generation mean analysis for backcross and F2 populations from eight hybrids, derived from two thin-pericarped sweet corn inbreds—AA8 and 677a (55 and 51 μm)—crossed with four field corn inbreds—B37, B68, H55, and Hi26 (range 82-132 μm). Average heterosis was −12.5% and segregating progeny distributions were skewed toward those of thin-pericarped parents. Narrow-sense heritability was high, averaging 55.2%, and the number of effective factors was low, ranging from 1.4 to 5.9 and averaging 3.3. Epistatic effects were as large as additive or dominance effects in many crosses, urging caution in applying models that exclude gene interactions to determine variance components and heritabilities. The mode of action in reducing pericarp thickness appeared to differ among the two thin parents, with AA8 affecting the differential thickening of germinal vs. abgerminal walls, and 677a reducing the number of pericarp cell layers. All genetic parameters suggested that genetic progress in backcross conversions to thin pericarp in sweet corn breeding would be rapid irrespective of the pericarp thickness of exotic parents.
Glenn M. Ito and James L. Brewbaker
Glenn M. Ito and Janies L. Brewbaker
In the paper “Genetic Advance through Mass Selection for Tenderness in Sweet Corn” by Glenn M. Ito and James L. Brewbaker (J. Amer. Soc. Hort. Sci. 106(4):496-499.1981) there are errors in the numbering of and textual references to the figures and tables. Table 1 on page 497 should be labeled Table 4, Table 2 on page 497 should be labeled Table 1, Table 3 on page 498 should be labeled Table 2, and Table 4 on page 499 should be labeled Table 3. Figure 1 on page 497 should be labeled Figure 3, Figure 2 on page 498 should be labeled Figure 1, and Figure 3 on page 498 should be labeled Figure 2. Accordingly, line 7 of the section beginning “Correlation of bite-test scores and pericarp thickness measurements” on page 498 should refer to Table 4; the last line on page 498 should refer to Figure 3; and line 8 of the first paragraph, second column, of page 499 should refer to Table 2. All other textual references correspond to the correct table and figure numbers as presented above.
Glenn M. Ito and James L. Brewbaker
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.