Analysis of heading date and grain yield for the effect of Ef-cd in 4 different latitudes including Beijing (39°54′ N, Beijing City), Jiaxing (30°75′ N, Zhejiang Province), Chengdu (30°42′ N, Sichuan Province), and Fuzhou (26°08′ N, Fujian Province). (A) Ef-cd NIL hybrid E-SY63 (ZS97A/D330) headed and matured earlier than the corresponding hybrid SY63 (ZS97A/MH63) in the 4 different latitudes. (B) Ef-cd NIL hybrid E-II-You838 (E-II-32A/FH838) headed and matured earlier than the corresponding hybrid II-You838 (II-32A/FH838) in the 4 different latitudes. Statistical comparison of the grain yields between SY63 and E-SY63 and II-You838 and E-II-You838 in (C) Beijing (sowing date was May 8, 2015), (D) Jiaxing (sowing date was June 30, 2015), (E) Chengdu (sowing date was May 15, 2015), and (F) Fuzhou (sowing date was June 18, 2015). The P value was calculated using Student’s t test. *P < 0.05; **P < 0.01; NS, not significant. (Scale bars, 20 cm.)