Early generation selection in 2 wheat crosses 2. F₃ line selection

Abstract

Direct selection for grain number per spikelet, grain number per ear, or weight per grain was more effective than selection for yield per se as indicated by direct responses and realised heritabilities. Yield per plant did not show any response to direct selection. The base population for selection was 40 F₃ lines of each of 2 crosses, derived by intense and fairly effective single plant F₂ selection for these yield components. F₃ line selection for grain number per spikelet gave positively correlated responses for most yield components and yield per plant at 2 planting densities in Hilgendorf × Oroua and at the higher density in Kopara × Oroua. Although grain number per ear and weight per grain compensated for each other, selection for grain number per ear in Kopara × Oroua resulted in positively correlated responses in yield components (except weight per grain) and yield per plant at high density. Selection for weight per grain in both crosses gave significant increases in yield/m-² at low density, mainly because of high ear number. The lack of significant positive correlations between the performance of populations at low and high densities for ear number and yield suggested a high level of genotype-environment interaction.