Comprehensive Evaluation on Cold Resistance of 8 PopulusStrains at the Seedling Stage

The annual cutting branches of 8Populusstrains were used to deal with 4 times of poikilothermic treatment ranging from -40 to 20℃in the early March 2016, the difference of germination rate after treatment was analyzed,it was concluded that the germination rate of each strain reached the maximum when treated 4 times. In March 2017, eightPopulus strains were treated with the same poikilothermic method on the cuttings of annual shoots, and the physiological and biochemical indexes of the cuttings were measuredThe indexes of 8 poplar strains were analyzed and evaluated by the correlation analysis, principal component analysis and membership function method to obtain the comprehensive index. According to the comprehensive index, the cold resistance of each strainwas ranked as below:P. pseudo-simonii>09-02-31>10-01-02>09-01-20>Liaohe× Zhong Sui 12> K99 >P. × deltoides‘Liaoyu3’>10-02-23. The 8 strains were divided into 3 categories by cluster analysis:P. pseudo-simonii and 09-02-31 as one class, their cold resistance was the strongest, while 10-01-02, 09-01-20, Liaohe×Zhong Sui 12, K99 and P. × deltoides‘Liaoyu3’ as another class, with stronger cold resistance,10-02-23 as separate classs, withthe weakest cold resistance.