Piriformospora indica promotes the growth and enhances the root rot disease resistance of gerbera

•P. indica significantly increased the transplanting survival rate of tissue cultured gerbera seedlings, and improved the aboveground fresh weight, underground fresh weight and chlorophyll content of the fungus colonized transplanted seedlings (PI).•Although P. indica showed no obvious antagonistic effect on Phytophthora cryptogea (the causal agent of gerbera root rot disease), P. cryptogea inoculated PI seedlings (PP) showed much milder diseased symptom compared with the P. cryptogea inoculated seedlings (PC).•P. indica appeared to improve the plant growth and confer gerbera with root rot tolerance through increasing POD, CAT and SOD activities and stimulating IAA and GA accumulation, and suppressing ABA and JA biosynthesis. P. indica can confer gerbera with root rot resistance.