Identification of index for detecting low-nitrogen tolerance in cucumber

The selection of cucumber (Cucumis sativus L.) cultivars with high capability for low-nitrogen (N) tolerance can reduce the production costs and environmental damage caused by N fertilization. The specific biomarker for the objective detection of low-N tolerance in cucumber has not yet been identified. In this study, cucumber chalcone synthase (CsCHS, Csa3G600020) was identified by Solexa sequencing. CsCHS exhibited a consistent upregulated expression pattern owing to low-N tolerance in two cucumber cultivars with different capabilities for low-N tolerance. Results of real-time quantitative polymerase chain reaction further showed that CsCHS had a consistent upregulated expression pattern induced by low-N tolerance in cucumber cultivars with different ecotypes and developmental stages. By referring to CsCHS expression, nitrate (NO3/sup -/) concentrations below 5 mM were identified as low-N tolerance in cucumber plants. Overall, results revealed that CsCHS expression was a stable index for detecting low-N tolerance in cucumber. (author)