Colonization with arbuscular mycorrhizal fungi mitigates cold stress through improvement of antioxidant defense and accumulation of protecting molecules in eggplants

Eggplant (Solanum melongena L.) is a thermophilic species susceptible to cold stress. The potential of arbuscular mycorrhizal fungi (AMF) for the amelioration of cold stress in this species has not been investigated so far. This study was conducted to examine some of the physiological functions through which the AMF colonization may improve cold stress tolerance in this species. Plants were inoculated with four AMF species (Funneliformis mosseae, Claroideoglomus etunicatum, Rhizophagus irregularis, and Diversispora versiformis), grown for three weeks under growth chamber conditions, and then treated with three different temperatures (25 degrees C, 15 degrees C, and 5 degrees C) for one week. Results showed that despite the reduction in root colonization, AMF were able to alleviate cold stress in the eggplants by improving photochemical reactions, activating antioxidant defense systems, accumulating protecting molecules, and reducing membrane damages. Cold stress mitigation through AMF was mediated by H2O2 as a priming molecule accumulated upon mycorrhization prior to cold stress. A comparison of four AMF species showed that D. versiformis was less effective than the other three fungal species in alleviating cold stress due to the inability to accumulate the protecting molecules, particularly proline and free phenolics. Our results revealed that AMF inoculation with suitable fungal species is an effective strategy for alleviating cold stress in eggplants.