Positive effects of co-inoculation with Rhizophagus irregularis and Serendipita indica on tomato growth under saline conditions, and their individual colonization estimated by signature lipids.

Tomato roots can be colonized by both mycorrhizal fungi and the endophytic fungus Serendipita indica. This study was aimed at assessment of the impact of single or dual inoculation with R. irregularis and S. indica on tomato growth under saline conditions. We used signature compounds to estimate the abundance of each of these two fungi (fatty acid 16:1ω5 for R. irregularis and ergosterol for S. indica) in roots. A randomized block design was applied with four types of inoculation (no fungus, R. irregularis, S. indica or S. indica + R. irregularis) at different levels of salinity (1.2, 5, and 10 dS/m) with four replications per treatment. The plant dry weight was slightly higher in R. irregularis- than S. indica-inoculated plants, and the highest plant biomass was achieved with dual inoculation. R. irregularis increased the content of the neutral lipid fatty acid 16:1ω5 from 97 to 5300 nmol/g and phospholipid fatty acid 16:1ω5 from 8 to 141 nmol/g in roots (at a salinity level of 1.2 dS m