Plant height in maize is not only one of impor-tant agronomic traits, but also one of model traits suitable for study of developmental biology. Using data from field tests in two locations (Wuhan and Xiangfan) within the same year and a molecular linkage map covering all of 10 chro- mosomes, QTLs affecting plant height at five different de- velopmental stages were mapped and analyzed by the com- bination of composite interval mapping and the conditional analysis method. Eight QTLs for plant height at different stages were located at different regions of five chromosomes (LOD≥2.5). The results showed that there were different effect values of QTL on plant height at different develop- mental stages. Three QTLs were detected at all of five stages. With different stages, contributory percentage of single QTL to plant height varied between 3.8% and 17.1%. It suggested that the expression of each QTL controlling plant height was different at different stages. With net growth, seven condi- tional QTLs for plant height were detected. Conditional QTLs were nearly detected at each stage, and QTLs of Ph1-1, Ph1-2, Ph3, Ph5-2 and Ph9 were detected at both locations (Wuhan and Xiangfan). The contributory percentage of sin-gle conditional QTL to plant height varied between 3.8% and 12.3%, indicating that QTLs for plant height are ex-pressed in different time-space. Therefore, QTL expressed at different stages should be considered when marker assistant selection is conducted for quantitative traits.
