Genetic and environmental considerations for evaluating crown position of wheat

Crown position affects winter survival of fallsown wheat (Triticum aestivum L.) Direct or indirect selection for crown depth has been little practiced. Reports have suggested that short subcrown internode length was closely related to semidwarf plant height and that semidwarfism was related to poor emergence. This study determined the relationships among crown depth, plant height, and emergence rate index in three wheat populations. The efficiency of evaluating crown placement in the field was examined and additional information was obtained on its genetic control. The F2-derived F4 and F5 lines from the crosses of female parents 'Daws', 'Nugaines', and 'Stephens' with male parent 'Selection 7952' were planted at Central Ferry and Pullman, Washington, respectively. Correlations from each population indicated that crown depth and subcrown internode length were not closely associated with plant height and emergence rate index. Crown depth was a more reliable indicator of crown placement than subcrown internode length. Adjustment of the data for seed depth differences was essential for evaluating subcrown internode length but less important for evaluating crown depth. After adjustment for seed depth, narrow-sense h (2) values for subcrown internode length and crown depth were 0.25-0.41. Crown depth and subcrown internode length were inherited as quantitative traits in phenotypes that expressed variable dominance. Modest gains due to selection for crown depth were achieved.