Genome-wide association study and metabolic pathway prediction of barrenness in maize as a response to high planting density oleh Xu-huan ZHANG, Hao LIU, Xu-hui MA, Gu-yi ZHOU, Hong-qiang RUAN, Hong-wei CUI, Jun-ling PANG, Ullah Siffat KHAN, Na ZONG, Ren-zhong WANG, Peng-fei LENG, Jun ZHAO