Corrigendum: Impact of Salicylic Acid and PGPR on the Drought Tolerance and Phytoremediation Potential of Helianthus annus - Khan, Naeem; Zandi, Peiman; Ali, Shahid; Mehmood, Asif; Adnan Shahid, Muhammad; Yang, Jianjun (Frontiers in Microbiology, 2019)