Assessment And Mechanism Study For Freezing Tolerance Of Potato Germplasm

Potato cultivars are sensitive to frost，they can be killed at temperatures below-2.5℃, and usually encountered early and late frost damage of which will result inpotato production reduction, even crops failure, and cause serious economic losses.Therefore, choosing the right screening method of frost resistance resources,screening out the resources, will provide a theoretical basis for resource evaluationof potato frost-resistant and cultivation of new varieties.In this dissertation, by measuring the semi lethal temperature, cold acclimationability and the change of physiological indicators before and after cold acclimationability of Qingshu9、Qingyin5、Shepody、E107、DR-2、DR-9、T3、A1、S4, wecan evaluate the frost resistance ability of the9materials and establish evaluationsystem of screening out frost resistance resources, research the changingcircumstance of potato seeding genomic Methylome before and after coldacclimation by using MSAP technology. The main results are as following:1. Using conductance method measure the LT50of various materials, To sortthe strength rank of the frost resistance ability before and after cold acclimation,according to the frost resistance ability of control group materials from strong toweak: DR-2＞DR-9＞A1＞T3＞S4＞E107＞Shepody＞Qingyin5＞Qingshu9；Thefrost resistance ability after cold acclimation from strong to weak: DR-2＞DR-9＞A1/Qingshu9＞T3＞E107＞Qingyin5＞S4＞Shepody；after cold acclimation of the9materials, the domestication ability of Qingshu9is3.6℃, Qingyin5is1.8℃, S4、Shepody、E107、A1、T3�'�DR-2do have domestication ability which is lower than1℃, DR-9is0.2. During cold acclimation, the proline content of potato material whose frost resistance ability is strong is lower than that of those who is weak, the growth of theproline content is larger for the material whose cold acclimation ability is strong;the MDA content increase before decrease then tend to stable status in general, it isnot obvious for the strong anti-freeze material during cold acclimation. On theseventh day of the cold acclimation, the content of strong acclimation material issmaller than the weak one; the SOD activity decrease in varying degrees for everymaterial, but the enzyme activity is the highest in Qingshu9、DR-2and DR-9, CATactivity decrease rapidly on the first day of cold acclimation and increase graduallybefore tending to stable, and its changing is not obvious for strong anti-freezematerial, weak anti-freeze material decrease larger on the first day, POD activity ofeach material tend to increase overall, the activity is higher for the strong anti-freezematerial than the weak one; finally concluded that the five physiological indexes canbe used as a potato index of frost resistance identification.3. The results of this study show that the low temperature stress can make DNAmethylation changes in different degree. Detected by MSAP methods, the potatogenome DNA methylation changes before and after cold acclimation, nine materialsproduced a total of94new methylation sites after cold acclimation,111demethylation sites, the phenomenon of methylation and demethylation has occurredboth, generally speaking, demethylation hold the main position.