Growth, Reproductive Performance, and Biomass Allocation of Dwarf Winter Wheat ‘Milyang54’ Under Dense Indoor Cultivation Conditions

Wheat ideotypes for dense indoor cultivation require compact architecture, maintained reproductive development, and sufficient biomass accumulation with high planting density and restricted rooting space. Milyang54 is an extremely short-stature winter wheat line developed as a candidate for space-efficient cultivation, but its response to indoor cultivation conditions differing in planting density and rooting space has not been characterized. In this study, Milyang54 and Jokyoung were grown with eight tray, pot, and spacing treatments in a speed-breeding greenhouse. These treatments were designed to generate contrasting planting densities and rooting-space conditions, ranging from low-density pot cultivation to high-density plug-tray and 1.5 cm spacing treatments. Agronomic and reproductive traits, shoot and root biomass, and root-to-shoot ratio were evaluated using a two-factor GLM with variety, cultivation treatment, and their interaction as fixed effects. Cultivation treatment significantly affected all measured traits, and significant variety × treatment interactions were detected for most traits. Across treatments, Milyang54 had a markedly lower mean plant height than Jokyoung (25.62 vs. 42.81 cm) but showed greater mean grain number per spike (11.03 vs. 7.51), shoot dry weight (25.85 vs. 21.58 g), and root dry weight (1.69 vs. 0.97 g). The grain-number advantage of Milyang54 was particularly evident in high-density and restricted-rooting-space tray treatments, including the 105-, 128-, and 162-cell trays. Root-to-shoot ratios varied among cultivation treatments, but a high ratio was not consistently associated with greater grain number. These results indicate that Milyang54 combines compact plant architecture with maintained reproductive performance and biomass accumulation under dense indoor cultivation conditions, suggesting its potential value as a compact wheat ideotype for controlled-environment agriculture.