1. State Key Laboratory of Crop Stress Biology for Arid Areas College of Life Sciences Northwest A&F University Yangling Shaanxi 712100 China
2. The Key Laboratory of Biology and Genetics Improvement of Maize in Arid Area of Northwest Region Ministry of Agriculture Northwest A&F University Yangling Shaanxi 712100 China
3. Biology Experimental Teaching Center College of Life Sciences Northwest A&F University Yangling Shaanxi 712100 China
4. Department of Horticulture, Seed Biology College of Agriculture, Food, and Environment University of Kentucky Lexington KY 40546 USA