Abstract:

In order to clarify the relationship between the nitrogen and the anthocyanin in cassava,we studied the agronomic traits and the inductions of anthocyanin synthesis-related genes and anthocyanin accumulation differences of cassava Arg7 sterile seedlings growing in the modified MS media for 40 d with 1）40 mmol/L NO₃^- + 20 mmol/L NH₄⁺,2）40 mmol/L NO₃^-,3）20 mmol/L NH₄⁺,4）0.4 mmol/L NO₃^- + 0.2 mmol/L NH₄⁺,5）0.4 mmol/L NO₃^-,6）0.2 mmol/L NH₄⁺,7）1 mmol/L（N）,8）5 mmol/L（N）,9）9 mmol/L（N）,and 10）13 mmol/L（N）,based on the previous research results of that nitrogen deficiency accelerates anthocyanin synthesis and accumulation in Arabidopsisetc. Results showed that no anthocyanin was observed in the seedlings of cassava variety Arg7 in any of the three modified MS media containing 40 mmol/L NO₃^- alone,20 mmol/L NH₄⁺alone or their combination for 40 d. Compared to cassava seedlings in the combination of 40 mmol/L NO₃^- and 20 mmol/L NH₄⁺,the plant height and length of primary roots under 40 mmol/L NO₃^- alone treatment were not significantly different,but the number of primary roots was significantly reduced. And the plant height,the length and number of primary roots of the seedlings in media with 20 mmol/L NH₄⁺ were significantly inhibited. The anthocyanins accumulated significantly in the stem and petiole of seedlings in any of three MS media supplemented with 0.4 mmol/L NH₄⁺,0.2 mmol/L NH₄⁺,or combination of 0.4 mmol/L NO₃^- and 0.2 mmol/L NH₄⁺ for 40 d,as well as genes related to anthocyanin synthesis were induced to be expressed. Compared to the combination of 40 mmol/L NO₃^- and 20 mmol/L NH₄⁺,the plant height,the lengths and the number of primary roots under MS media with 0.4 mmol/L NO₃^-,0.2 mmol/L NH₄⁺,or combination of 0.4 mmol/L NO₃^-,and 0.2 mmol/L NH₄⁺ significantly decreased,but the anthocyanin content significantly increased. Furthermore,there was a negative correlation between anthocyanin content and nitrogen concentration（R²=0.96）. This indicates that the induced expression of anthocyanins in cassava Arg7 seedlings was only related to nitrogen concentration,but not to the form.

Key words: anthocyanin, cassava, nitrogen concentration, nitrogen form, gene expression