Ethylenediurea Reduces Grain Nitrogen but Enhances Protein and Carbon Yield in Rice Cultivars

Ethylenediurea (EDU) is an indicator of surface ozone (O-3), has a high potential to be developed as an applicable protectant for crops against O-3 phytotoxicity. Studies on the effects of EDU on grain quality are few, limiting evaluation of the efficiency of EDU protection. In order to understand the effects of EDU on grain quality in rice, a field study was conducted in a rice paddy, where EDU solutions were foliar applied to rice plants. At maturity, grain nitrogen concentrations (GN) in 21 rice cultivars and related traits were analyzed. Mean across 21 cultivars, GN was reduced by EDU by 3.81%, suggesting that O-3 in ambient air is affecting grain quality. GN negatively correlated with grain weight and source/sink ratio, but positively correlated with spikelet density. Moreover, GN changes to EDU were rice type dependent, which were -0.43%, -0.72%, and 1.19% in indica, japonica, and hybrid rice, respectively. These results suggest that EDU promotes sink in rice, which helps to increase grain yield, but allocation of nitrogen is not enough to maintain GN in both indica and japonica cultivars. Rice types and cultivars' variations in the responses of GN to EDU highlight a possibility to adjust grain quality by EDU, combining cultivar selection and agricultural management in response to surface O-3 pollution.

Automated summary

Ethylenediurea (EDU) is a potential protectant for crops against surface ozone (O-3) phytotoxicity. A field study on rice plants showed that EDU reduced grain nitrogen concentrations (GN) by 3.81%, suggesting that ambient O-3 affects grain quality. The effects of EDU on GN were rice type dependent, with decreases of -0.43%, -0.72%, and increases of 1.19% in indica, japonica, and hybrid rice, respectively. EDU promotes sink in rice and increases grain yield, but indica and japonica cultivars have insufficient nitrogen allocation to maintain GN. The results highlight the possibility of adjusting grain quality by EDU in response to surface O-3 pollution, through cultivar selection and agricultural management.