国家自然科学基金No.41171203;陕西省科技统筹创新工程计划项目No.2011KTCL02-15;公益性行业农业科研专项No.201303094Supported by the National Science Foundation of ChinaNo.41171203,the Innovation of Science and Technology Plan Projects of Shaanxi Provionce No.2011KTCL02-15 and the Special Fund for Agro-scientific Research in the Public Interest No.201303094