Relationship between Canker-tolerance and Spring-freezing Tolerance of Poplar Clones

To find out the inducing cause for poplar canker,the changes of relative conductivity and branch vitality of sprouting and dormant branches of ll poplar clones were measured under freezing condition. The results showed that under -5～-25℃ freezing condition,the changes of relative conductivity of the sprouting branches were significant.Among the ll poplar clones,the increase of relative conductivity and decrease of branch vitality were obviously relevant to the increase of infection rate and infection index of the clones.Therefore,the spring-freezing tolerance of the sprouting branches was negatively relevant to the canker tolerance of the clones.The changes of relative conductivity and branch vitality of dormant branches were not obvious and they had nothing to do with their canker tolerance.