Correlation between soluble sugar and tolerance to drought stress of cassava stem under low temperature storage

Objective  The changes of water loss status, soluble sugar content and relative enzyme gene expression in related glyco metabolism signal pathway of cassava stem under different storage temperature and time were studied, and the correlation between trehalose content and water loss rate of cassava stem was analyzed.

Method  The stem of ‘cassava 60444’ was used as the experimental material. The stem was stored under low temperature of (20±2)℃ and normal temperature of (36±2)℃ for 0–30 d after harvest. The water loss status and soluble sugar content were determined, the change of related enzyme gene expression in the signal pathway of sugar metabolism was analyzed by real-time fluorescence quantification PCR, and the correlation between trehalose content and water loss rate of cassava stem was analyzed by Pearson method.

Result  The water loss rates of cassava stem in low temperature storage group at 10, 20, 30 d were significantly lower than those in normal temperature storage group (P<0.01). The trehalose contents of cassava stems under low and normal temperature storage overall increased to different degrees with the extension of storage time, and the content of low temperature storage group was significantly lower than that of normal temperature storage group at 10, 20, 30 d (P<0.05). The contents of sucrose, glucose, fructose and maltose in low and normal temperature storage groups all showed a decreasing trend with storage time. Correlation analysis showed that there was a strong linear correlation between trehalose content and water loss rate in low and normal temperature storage groups, and there was significant difference in the regression equations between the two storage groups with the smaller correlation coefficient under low temperature storage. Real-time quantitative PCR analysis showed that the expression of glycolysis related genes increased under low and normal temperature for 10–30 d, most related genes in low temperature storage group had lower expression level, and the expression of trehalose-6-phosphate synthase gene (METPS-1) at 10, 20, 30 d was significantly low than that in normal temperature storage group (P<0.05).

Conclusion  Low temperature storage of cassava stem contributes to retaining water, slowing down glycolysis rate and prolonging storage time. There is a strong correlation between trehalose and water loss stress of cassava stem, and the increase of trehalose content is helpful to improve the water retention capacity of cassava stem.