Acknowledgement

We thank Drs.S.J，Sheen.J.Berbec，Prof.L.Burk.and Mr.G.W.Pittarelli for their generosity of supplying the male sterile seed.This work was supported by NSF grant PCM-7812126，NIH grant GM27746-01 and USDA Cooperative agreements 12-14-1001-967 and 12-14-1001-810.(https://www.daowen.com)