Isogenic Heading Data Effects on Yield Component Development in ‘Titan’ Barley 1

Crop adaptation in the Rocky Mountain northwest is strongly dependent on proper heading date. A series of six isogenic lines of ‘Titan’ barley ( Hordeum vulgare L.) were developed by backcross techniques to determine the specific effect of genetically controlled heading date differences on barley yield and yield component responses. The isotypes were grown in 15 Montana environments using commercial planting rates, and in one space‐planted environment. Strong mean yield component compensation and nonsignificant yield differences among the isotypes over the drill‐planted environments were revealed by correlation analysis. Increases in all yield components and yields with later heading isotypes were found in the low‐stress, space‐planted environment. Correlations among yield and the yield components over the drill‐planted environments (stress matrix) revealed significant correlations of the yield components to heading dates, but not to yield. Correlation matrices in each environment revealed that late heading isotypes consistently developed more kernels per spike and had lower kernel weights than the early heading isotypes in most environments. Stability analysis of each isotype against the mean of each environment revealed consistent significant isotype ✕ environment interactions for spikes per square meter, few significant interactions for kernel weight, and no interactions for kernels per spike or yield among the six isotopes. This study detailed the effect of genetic maturity on yield component development over a large number of environments. The consistent kernels per spike response among the isotypes implies that yield improvements in early lines may be gained by positive selection for this character.