Evaluation of cold tolerance of sugarcane under drought frost condition.

[Objective]The aim was to understand the change characteristics of sugarcane traits and evaluate the cold tolerance of sugarcane varieties under the drought and frost conditions.[Method] The experiment was carried out in Ziyuan County,Guangxi Province where the frost occurred often with 21 domestic and abroad sugarcane varieties(elites).[Result] There were significant changes in the brix,green leaf number and photosynthetic rate of sugarcane before and after light frost and decreased more in cold-sensitive varieties.However,the correlation was only significant between the damage rate of stem length and internode,percentage of green leaves after heavy frost in relation to sugarcane brix and brix changes after light frost.Further analysis showed that the evaluation for cold tolerance of sugarcane would be more simple and reliable with traits of the damage rate of stem length and percentage of upper green leaves.The evaluation for varieties indicated that if it was not carried out for cold-tolerance identification in breeding program,the percentage of sugarcane varieties with good cold-tolerance will be lower than30%,and higher than 60% with poor cold-tolerance in subtropical and tropical regions.[Conclusion] This study had provided theoretical basis for the cold-resistant evaluation of sugar cane and the breeding of the varieties of cold-resistant.