title: Response to Dr. Robertson's Letter to the Editor.
authors.affiliation: Jiangsu Academy of Agricultural Sciences, Institute of Vegetable Crops, Nanjing 210014, Jiangsu, People's Republic of China (ququzhibao@126.com.
authors.forename: S X
authors.initials: SX
authors.lastname: Qu
authors.affiliation: qusx@jaas.ac.cn).
authors.forename: J D
authors.initials: JD
authors.lastname: Song