AMF improves response to waterlogging stress in cucumber

This study aimed to examine whether and how an arbuscular mycorrhizal fungus, Paraglomus occultum, affected the growth performance, antioxidant enzyme defense system, and expression levels of fourteen plasma membrane intrinsic protein (PIP) genes of cucumber seedlings after five days of waterlogging. The fungal treatment significantly increased growth rate of plant height and stem diameter, root length, and root surface area under waterlogging. Inoculation with P. occultum significantly boosted superoxide dismutase, peroxidase, and catalase activities under waterlogging, enabling inoculated plants to maintain low levels of hydrogen peroxide and malondialdehyde. The waterlogging up-regulated the expression of more CsPIP genes in inoculated versus uninoculated plants. Interestingly, four of fourteen CsPIP genes were down-regulated under no stress by P. occultum, and seven were up-regulated under waterlogging, implying that inoculated plants actively responded to waterlogging stress by up-regulating the expression of CsPIP genes. This study confirmed that P. occultum increased waterlogging tolerance in cucumber plants, which was associated with enhanced antioxidant enzyme defense system and up-regulation of CsPIP genes.