Screening Of Physiological Indexes Of Cold Resistance And Establishment Of The Method For Identifying Cold Resistance In Camellia Sinensis

In this study，we detected4physiological indexes that included the Relative Electric Conductivity(REC), MDA content, soluble sugar content and proline content in leaves of Shuchazao and Wuniuzao under artificial low temperature conditions and natural low temperature conditions. The result showed that there was a high negative correlation between the change of soluble sugar content and the change of temperature either in artificial low temperature conditions or in natural low temperature conditions by comparing and analysing the regularity of changes of the four indexes with the temperature. As the temperature fell, the soluble sugar content showed a significant and single increasing trend, which had a good regularity of change. So compared with other indexes, the soluble sugar content in leaves of Camellia sinensis can better reflect the physiological change of Camellia sinensis under cold stress.To further understand the regularity of the accumulation of the soluble sugar content under low temperature, this study utilized HPLC technology to detected the compositions of the soluble sugar in leaves of Shuchazao and Wuniuzao under natural low temperature conditions. By comparing the dynamic change of various sugars, we found sucrose accounted for dominant position in the compositions of the soluble sugar in leaves of Camellia sinensis, and there was a high negative correlation between sucrose content and monthly average temperature. As the temperature fell, the sucrose content showed a significant increasing trend, and there were a large differences in the rate of increase between Shuchazao and Wuniuzao. The sucrose content of Shuchazao that had stronger cold resistance in production practice increased from23.13mg/g (dry weight) to137.03mg/g (dry weight), increased by5times. The sucrose content of Wuniuzao that had weaker cold resistance in production practice increased from42.46mg/g (dry weight) to112.14mg/g (dry weight), increased by2times. In addition, on low-temperature months (December, January and February), the sucrose content of Shuchazao was significantly higher than that of Wuniuzao. Based on this conclusion, this study aimed to provided a theoretical basis for establishing a method that can identify the cold resistance of Camellia sinensis by detecting the sucrose content in leaves of different various of Camellia sinensis. After confirming the close relationship between the accumulation of sucrose content and the cold resistance of Camellia sinensis, the study on Sucrose Phosphate Synthase (SPS) that is the key enzyme of regulating the synthesis of sucrose and the SPS gene will help to understand the relationship between sugar metabolism and cold resistance of Camellia sinensis. In this study, we cloned full-length cDNA of SPS of Camellia sinensis. The sequence analysis showed that the SPS gene called CsSPS contained3635bp and coded1036amino acid residues. Compared with Solanum tuberosum, Coffea canephora, Cucumis melo, Nicotiana tabacum, Prunus persica and Solanum lycopersicum, the homology of its amino acid sequence reached above80%. This work will supply some necessary information for further study on the expression of CsSPS under cold stress.