Effect of irrigation with microcystins-contaminated water on growth and fruit quality of Cucumis sativus L. and the health risk

Microcystins (MCs) are released into the lake during the outbreak of cyanobacteria and could enter the farmland ecosystem by irrigating. This study investigated the effect of MCs on growth, yield and fruit quality of cucumber and evaluated the potential risk of MCs. Cucumber plants were irrigated daily for 7 days with MCs extraction contaminated water (0, 1, 10, 100, 1000 μg/l), and then, cultivated with uncontaminated water to final harvest. Results show that 10 μg/l MCs exposure inhibited the growth of cucumber at different growth stages, and the order of decreased degree in the growth of cucumber was seedling stage > early flowering stage > fruiting stage. Contents of vitamin C, soluble sugar and organic acid in fruits of cucumber exposed to10 μg/l MCs at seedling stage were decreased. MCs at concentrations of 100 μg/l and 1000 μg/l significantly decreased the growth of cucumber at different growth stages, and reduced cucumber yield at fruiting stage. There were even no fruits at seedling stage and early flowering stage. The estimated daily intake of MCs in fruits exposed to 100 μg/l and 1000 μg/l MCs at fruiting stage were 0.103 μg/kg and 0.198 μg/kg, exceeding WHO limit. It indicates that human should exercise care when ingesting cucumber fruit as a part of their diet and strengthen agricultural irrigation management to prevent cucumbers from irrigating with MCs contaminated water.