Divergent Mass Selection for Grain Protein in Sorghum1

Abstract

The low, and often variable, protein percentage of sorghum [Sorghum bicolor (L.) Moench] grain is a constraint to utilization of the crop as feed or food. A study was undertaken to determine the effectiveness of fertile plant mass selection for high and low protein percentage in a sorghum random‐mating population under standard field production practices of eastern Nebraska. Four cycles of positive selection increased grain protein content 0.50 percentage points from the base (10.93%), and negative selection decreased it 1.06 percentage points. Calculated heritabilities for high and low protein selection were 0.16 each, but realized heritabilities were 0.10 and 0.19, respectively. Protein yield remained nearly constant regardless of the selection direction. Although grain yields of the base and the selection cycles were not statistically different when all were tested together, a trend existed toward lower yields in the high protein cycles and higher yields in the low protein cycles. An overall phenotypic correlation of −0.86 existed between grain yield and protein percentage. The study demonstrated that mass selection was somewhat effective in changing grain protein percentage, but large positive gains for protein content would be difficult to obtain in common sorghum germplasm without accompanying negative effects on yield. Utilization of protein‐specific genes and index selection may be necessary to attain desired plant breeding goals.