Relationship of Black Layer to Sorghum Kernel Moisture Content and Maximum Kernel Weight in the Tropics1

Three male lines of sorghum [Sorghum bicolor (L.) Moench] were each crossed onto three female lines to produce nine hybrids. These hybrids and the three male lines were used to study the relationship between black layer formation and maximum dry weight and moisture content. Kernels were collected from the top, middle, and bottom portions of sorghum panicles at two stages of maturity to obtain two samples of kernels before and two samples after black layer formation. The object of this study was to determine if black layer formation could be used as an index of moisture content and of physiological maturity under tropical conditions.Black layer formation and maximum dry weight occurred at the same time or within one maturity stage in most cases. Moisture content of the kernels at black layer formation varied with hybrids and lines. Fully matured kernels of the hybrids were not always the same weight from top, middle, and bottom portions of the panicles. For some hybrids, the top kernels were larger, and for others the bottom kernels were larger. The bottom kernels from two of the three lines were smaller than those from the middle portion of the panicle. To avoid difficulty in interpreting data, one should sample one portion of the sorghum panicle consistently.