Progress of super hybrid rice research in China

To meet the growing food demands in China, a program of super rice breeding was set up by the Chinese Ministry of Agriculture in 1996. The goals of this program is to achieve rice yield targets to 10.5, 12.0, 13.5, and 15.0 t/ha in single season rice growing area through four research phases. A proposed model of combining morphological improvement with the utilization of inter-subspecific (indica/japonica) heterosis, by Prof. Yuan LongPing in 1997, played a leading contribution for the program of super hybrid rice breeding. Until now, all yield targets of four phases have been achieved. The pioneer super hybrid rice variety, Liangyoupeijiu, met the Phase I yield target in 2000. The Phase II super hybrids were successfully developed in 2004. Y Liangyou No.1 (YLY1), the typical Phase II super hybrid rice variety, has a largest annual planting area among all hybrid rice varieties in China since 2010 and has been extended to more than 4 million hectare so far. Y Liangyou No.2 (YLY2) met the standard of phase III super rice with a yield record of 926.6 kg/mu (13.9 t/ha) in 2011. The breeding target of Phase IV super hybrid was achieved in 2014. The new variety, Y Liangyou 900 (YLY900), created a new yield record of 15.4 t/ha, which doubled the average rice yield in China. Up to now, 125 super rice varieties have been certificated by the Ministry of Agriculture with a total planting area of approximate 80 million hectare in China. However, how to further break the yield ceiling and realize the yield potential of elite varieties in diverse range of target environments remains to be the major challenges for super hybrid rice breeding. Herein, we proposed that utilization of ideotype and inter-subspecific heterosis, assisted with molecular design breeding, is still being the vital way to increase yield ceiling.