Effects of Daylength Response and Semidwarfism on Agronomic Performance of Spring Wheat 1

Semidwarfism and daylength insensitivity have advantages for winter increase in southern latitudes and to allow wider potential use in breeding programs around the world. To determine if these traits have adverse effects in the upper Midwest, the progenies from a cross of ‘Justin,’ a tall daylength‐sensitive spring wheat ( Triticum aestivum L.), by ‘Ciano 67,’ a semidwarf daylength‐insensitive cultivar, were separated into four phenotypic classes: tall‐insensitive (TI), tallsensitive (TS), semidwarf‐insensitive (DI), and semidwarf‐sensitive (DS). Each phenotypic class was represented by 28 F6 lines, randomly derived with the exceptions of their response to daylength and plant height. The lines were grown in three environments after normal time of seeding and one environment after late seeding to obtain information on the effects of semidwarfism and daylength‐insensitivity on various traits in different environmental conditions. As expected, the insensitive classes headed earlier than the sensitive classes, while the tall classes and semidwarf classes headed similarly. The sensitive classes were slightly taller than the insensitive classes. The tall classes yielded more than the semidwarf classes in the two environments where yields were highest but did not differ over all locations. The sensitive classes were superior to the insensitive classes in three of the four environments, but they did not differ following late‐seeding. Individual high‐yielding lines were observed in each phenotypic class, except in the TI class. The DS class had considerably lower test weight than all other classes. However, reduced test weight did not appear to be closely associated with semidwarfism since the DI class had test weight equal to the mean of the two tall classes. The DS class was lowest in protein percentage, but the DI class was equal to the TS class. Thus lower protein percentage did not appear closely related to the semidwarf trait. Late seeding did not reduce the performance of the semidwarf or the insensitive classes relative to the other classes. The TS and DI classes represented parental types and apparently had higher frequencies of favorable gene combinations for yield. Consequently, for future studies, intercrossing may be beneficial to help distribute favorable gene combinations. Using these genetic materials, no severe deleterious effects were observed to be tightly associated with semidwarfism or daylength‐insensitivity.