Effect of nitrogen application on carbon and nitrogen metabolisms and relationship between carbon metabolism and wheat scab

To clarify the characteristics of carbon and nitrogen metabolism in wheat plants under different nitrogen application and the relationship between carbon metabolism and wheat scab, a field experiment was conducted in Yuzhou County of Henan Province using 5 nitrogen rates of 0 kg(N) hm^-2, 120 kg(N) hm^-2, 180 kg(N) hm^-2, 240 kg(N) hm^-2, 360 kg(N) hm^-2 and two winter wheat genotypes of multi-spike cultivar 'Yumai49-198' (YM49-198) and big spike variety 'Zhoumai16' (ZM16). The results indicated that the soluble sugar content and C/N from wintering to flowering stages showed a "V" type, and was lowest at jointing stage, with the lowest values of 80-200 mg·g^-1 and 3-10, respectively, for two cultivars. The maximum differences among different treatments appeared at flowering stage, when the soluble sugar content and C/N of nitrogen treatments were 15.4%?47.7%, 24.5%?63.1%, respectively, lower than those of the non nitrogen treatment. The total nitrogen content increased with the increase of nitrogen application rate, and difference among treatments reached the maximum at jointing and flowering stages. The accumulation of soluble sugar and nitrogen showed an increasing trend. Correlation analysis showed that the total nitrogen content at jointing and flowering stages were significantly negatively correlated with soluble sugar content. The soluble sugar content, C/N at jointing and flowering stages showed a linear relationship with wheat scab incidence and disease index. This indicated that the carbon and nitrogen metabolism from jointing to flowering stages had a greater impact on the scab of wheat.