Positive effects of co-inoculation withRhizophagus irregularisandSerendipita indicaon 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 fungusSerendipita indica. This study was aimed at assessment of the impact of single or dual inoculation withR. irregularisandS. indicaon tomato growth under saline conditions. We used signature compounds to estimate the abundance of each of these two fungi (fatty acid 16:1 omega 5 forR. irregularisand ergosterol forS. indica) in roots. A randomized block design was applied with four types of inoculation (no fungus,R. irregularis,S. indicaorS. 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 inR. irregularis- thanS. indica-inoculated plants, and the highest plant biomass was achieved with dual inoculation.R. irregularisincreased the content of the neutral lipid fatty acid 16:1 omega 5 from 97 to 5300 nmol/g and phospholipid fatty acid 16:1 omega 5 from 8 to 141 nmol/g in roots (at a salinity level of 1.2 dS m(-1)), but the increases were lower at higher levels of salinity. Moreover, both these arbuscular mycorrhizal fungal markers were slightly decreased in the presence ofS. indica.Root ergosterol increased from 7 to 114 mu g g(-1)withS. indicainoculation. With increasing salinity, the concentration of ergosterol in roots decreased. Inoculation withR. irregulariscaused a decrease in root ergosterol. Increasing salinity resulted in an increase of Cl and Na in tomato shoots, but the increase was significantly lower in single- or dual-inoculated plants in contrast to the control plants.