Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Plant Breeding

First Advisor

Thomas Lubberstedt


Brassinosteroids (BRs) and gibberellins (GAs) are two major plant hormones involved in many plant developmental processes. However, the knowledge of BR and GA control of agronomic traits in maize is limited compared to model species Arabidopsis and rice, especially BR. This PhD project focused on BR and GA control of plant height from genetics and plant biology perspectives, as these two plant hormones have shown great impact for shaping plant height, and a short/tall stature of maize height is beneficial for grain/biomass production, respectively. We introgressed multiple exotic accessions into two maize heterotic groups Stiff Stalk and Non Stiff Stalk, with phenotype selection for taller plant height and undistinguishable flowering time as temperate elite lines. Finally, we created two backcross libraries varied with plant height and the level of heterozygosity. Moreover, another two doubled-haploid libraries were established without any phenotype selection as a comparison. We conducted genome-wide association studies to investigate plant height, BR and GA candidate genes, and explored co-localizations. In addition, we compared BR and GA control of plant height in heterozygotes (backcross families) and inbred lines (doubled haploid lines) by correlating seeding BR/GA inhibitor response with field plant height. We found that discovered plant height associated genomic regions were overlapped with BR and GA candidate genes. Moreover, we found that seedling stage BR and GA inhibitor response was able to predict plant height for heterozygotes, but not inbred lines. Path analyses showed that higher level of heterozygosity increased GA level, and GA promoted BR (by crosstalk), finally BR and GA will increase heterosis in maize plant height.


Copyright Owner

Songlin Hu



File Format


File Size

225 pages