Serendipita indica is a biostimulant that improves tea growth at low P levels by modulating P acquisition and hormone levels

Serendipita indica (S.i.) exhibits mycorrhizal fungus-like characteristics, while it is unclear how S.i. improves root growth of tea seedlings at low phosphorus (P) levels. This study investigated the effects of S.i. on biomass production, auxin and cytokinin levels, root P levels, soil Olsen-P levels, soil phosphatase activities, and root P transporter (PT) gene expression in tea (Camellia sinensis) seedlings at normal (50 mM P) and low (0.5 mM P) P levels. S.i. colonized tea roots. S.i. inoculation significantly increased shoot and root biomass production at low and normal P levels, as well as root indolebutyric acid, isopentenyladenine, and trans-zetin levels at low P levels. Furthermore, S.i. inoculation significantly raised root P and soil Olsen-P levels at low and normal P levels, accompanied with an increase in soil acid and neutral phosphatase activities at low P levels. S.i. inoculation increased root CsPT1 expression at low P levels. In summary, S.i. can be considered as a biostimulant to improve tea growth and root P acquisition at low P levels.