Selecting for Grain Protein and Yield in Sorghum Random‐Mating Populations1

Abstract

Grain protein and grain yield relationships were studied in six sorghum [Sorghum bicolor (L.) Moench] populations tracing to the same base but developed with different objectives. Two cycles of selection for high and low grain protein in NP7BR were evaluated in Nebraska with 200 S1 progenies each that arose from intermating mass‐selected fertile plants. Means, variance components, heritabilities, genetic and environmental correlations, and expected correlated responses were determined. The same information was collected on 150 S1 progenies each from the related populations, NP7BR and NP9BR, selected for grain yield in Nebraska and for drought tolerance in Arizona, respectively.Change from the first selection cycle to the second selection cycle was significant by mass selection for both high and low grain protein percentage in NP7BR. The 0.4% gains in either direction were about one‐half of those predicted, and protein and grain yield had strong negative genetic correlations (− 0.42 to − 0.65). Populations selected for grain yield produced more protein per ha (protein yield) than did populations selected for protein. In all populations, the expected correlated response of protein or of yield was negative when the other trait was selected. Protein percentage showed little correlated response with selection for protein yield except in NP7BR. Selection for protein yield would be expected to result in yield advances equal to selection for yield per se without drastic decreases in grain protein, but high environmental correlations between grain yield and protein yield would exist.