Growth Promotion and Salt-Tolerance Improvement of Gerbera jamesonii by Root Colonization of Piriformospora indica

Interaction of plants with beneficial microbes is one of the strategies for increasing growth and resistance under environmental stresses. In this study, the effects of a fungus, Piriformospora indica, on growth and salt resistance in gerbera (Gerbera jamesonii L.) seedlings were investigated. After co-cultivation with P. indica, the gerbera roots were colonized by the mature chlamydospores of P. indica. A large increase in plant biomass and enhanced photosynthesis were observed in the P. indica-colonized seedlings. Moreover, these seedlings also exhibited a strong tolerance to salt stress after the colonization. The wilting symptoms, the impairments in chlorophyll, carotenoids, and photosynthesis, and anthocyanin accumulation, that can be caused by salt stress, were alleviated in the P. indica-colonized plants. The malondialdehyde and hydrogen peroxide levels were lower in P. indica-colonized plants than in non-colonized plants under salt treatment, whereas both enzymatic and non-enzymatic antioxidants were not increased by P. indica colonization. Differential expressions of sodium transporter genes and aquaporin genes were found in gerbera plants after P. indica colonization. The P. indica colonization positively regulated the transcription level of genes involved in ionic homeostasis, such as NHX2 and SOS1, while most aquaporin genes were not induced in P. indica-colonized gerbera seedlings exposed to salt stress, except for NIP6;1 gene. These results demonstrate a strategy through plant-microbe interaction to promote Gerbera jamesonii performance under salt stress.