Pericarp thickness of a shrunken-2 population of maize selected for improved field emergence

While the pericarp of maize (Zea mays L.) protects the kernel from pathogens, a thin pericarp is desirable in imparting tenderness in sweet corn. The objective of this study was to determine the correlated response in pericarp thickness due to selection for improved field emergence and seed weight in a shrunken-2 (sh2) population. Two experiments were performed on a population to determine this relationship. In the first experiment, pericarp thickness of 11 cycles of a sh2 population mass selected for improved field emergence and increased seed weight was examined. Thickness of excised pericarps from mature kernels was measured with a pressure micrometer. Field emergence was determined in replicated trials in Urbana, IL in 1986 and 1987. Although significant differences in pericarp thickness were found, they were not correlated with field emergence. Little of the variation in pericarp thickness was due to linear trends resulting from indirect selection (r² = 0.15). In the second experiment the pericarp thickness was examined on kernels from 100 ears from each of Cycles 2, 5, 8, and 11 of the same sh2 population. The differences in pericarp thickness among cycles, although significant, were small and did not reflect linear trends related to cycles of selection (r² = 0.10). Selection for improved field emergence and seed weight in this sh2 maize population did not alter pericarp thickness. Thus, field emergence of sh2 sweet corn may be improved without increasing pericarp thickness and decreasing tenderness.