Impact of dark septate endophytes on tomato growth and nutrient uptake

Background: Dark septate endophytes (DSEs) represent a form-group of ascomycetous fungi that inhabit the roots of a wide range of plant species, but our knowledge on their interaction with the host plants is still limited.Aims: This study was conducted to examine the effect of DSEs on the nutrition and growth of tomato (Solanum lycopersicum) in order to assess their potential application in horticultural plant production.Methods: The capacity of two model DSE species, Periconiamacrospinosa and Cadophora sp. to mobilise different forms of N and P (organic and inorganic) was analysed, and an in vitro bio assay with tomato plantlets was applied to screen the compatibility of these fungi with the plant. Pot-culture experiments with and without compartments were conducted to study the effects of these DSEs on the growth and nutrient uptake of tomato plants grown with organic and inorganic N and P sources.Results: Periconia macrospinosa, but not Cadophora sp., increased the root and shoot biomass of tomato plants when organic nutrient resources were present, and both DSEs promoted shoot growth when cultivated with inorganic fertilisers. Analysis of N and P concentrations indicated that the growth response of tomato with inorganic fertilisation was not based on DSE-improved plant nutrition. However, P. macrospinosa improved N uptake from organic sources.Conclusion: The positive effects of DSEs seem to be due to nutrient mobilisation rather than to hyphal transport to the plant.