Effect of nitrogen levels on the changes of phenol and flavonoid contents under rice monocropping and intercropping system

Plant N nutrition is important for plant metabolisms and its resistance to plant diseases. Two rice varieties with different resistance to rice blast, Huangkenuo(HKN) and Hexi-41 (HX41), were used to investigate the effect of nitrogen fertilizer rates on the changes of phenol and flavonoid contents in Huangkenuo rice plant and on its relationship to rice blast occurrence under rice monocropping and intercropping system. Results showed that high nitrogen level (N 300 kg/ha) reduced the biomass, yield, phenol and flavonoid contents in rice leaves, but increased the rice blast severity index, especially in monocropping Huangkenuo. Under rice intercropping treatment, high nitrogen rate had no significant effect on the yield and phenol content. However, the reduction of flavonoid content and increase of rice blast incidence were not as significant as in rice with the monocropping treatment. Under low nitrogen level, Hexi-41 and Huangkenuo intercropping increased the biomass, yield, phenol and flavonoid contents and decreased the occurrence and severity of rice blast. Results also suggested that negative correlation existed between the contents of phenol and flavonoid in leaves, and the rice blast incidence.