Objective  To investigate the changes of starch content, reducing sugar content and soluble total sugar content in tubers, the changes of endogenous hormone content in tubers, the morphological indexes, physiological indexes and the analysis of variance of endogenous hormones during the process of tuber expansion. And the correlation between these indicators and endogenous hormones, lay the foundation for further study of the physiological mechanism of yam growth and development and guiding the high yield and quality cultivation of yam.

  Method  Six kinds of endogenous hormones such as ABA, GA3, IAA, JA, ZR and IPA were determined by enzyme-linked immunosorbent assay with different tuber lengths of Bikeqi yam. High performance liquid chromatography (HPLC) was used to determine the content of salicylic acid (SA), and to analyze the dynamic changes of source hormone content in different growth stages, and the correlation between morphological indicators of yam and endogenous hormones. The relationship between differentially expressed genes associated with endogenous hormones and endogenous hormones was explored for the effects of these factors on the expansion of yam tubers.

  Result  The contents of IAA, ZR, ABA, JA and SA were positively correlated with the morphological indexes of yam tuber; the contents of GA3 and IPA were negatively correlated with the morphological indexes; the contents of IAA were positively correlated with the perimeter and diameter of yam tuber; the contents of GA3 were negatively correlated with the length of tuber; the genes correlated with IAA were negatively correlated with the contents of IAA

  Conclusion  Endogenous hormones IAA, ZR, ABA, JA and SA promote the expansion of yam tuber; endogenous hormones GA3 and IPA inhibit the growth of yam tuber; endogenous hormones IAA promote the thickening of yam; endogenous hormones GA3 inhibit the elongation of yam; the down-regulation of IAA related genes can promote the synthesis of IAA, that is, regulate the content of IAA.