Comprehensive Evaluation of Aluminum Tolerance in Sugarcane Varieties at the Seedling Stage and Screening of Identification Indexes

[Objectives]Aluminum toxicity is one of the important stress factors affecting sugarcane quality and yield in south China,breeding aluminum tolerant varieties is a cost-effective and practical way.In order to explore the characteristics of aluminum toxicity tolerance in different sugarcane varieties and establish the comprehensive evaluation system for screening and breeding new varieties with aluminum toxicity tolerance,this study was conducted to perform comprehensive evaluation of aluminum tolerance in different sugarcane varieties and screening of identification indexes.[Methods]With 26 sugarcane varieties bred in different ecological areas as materials,through a pot experiment,nine indexes which include sugarcane plant height,root length,shoot dry weight,root dry weight,root-shoot ratio,relative chlorophyll content,leaf proline content,and shoot and root aluminum contents at the seedling stage under acid-aluminum stress and control conditions were measured,and the aluminum toxicity tolerance coefficients of various indexes of each variety were calculated.On this basis,the aluminum tolerance of all varieties was comprehensively evaluated by principal component analysis,subordinate function,cluster analysis and stepwise regression analysis.[Results]Compared with the control,the nine indexes showed more abundant variation among the 26 varieties under acid-aluminum stress.The correlation analysis confirmed that the contributions of the nine measured indexes to aluminum tolerance were significantly overlapped,and the subsequent principal component analysis summarized and combined the ones with strong correlation among the nine indexes,converting them into two new independent comprehensive indexes.The cumulative contribution rate showed that the two new indexes covered 82.448%of the information of the original nine indexes.Then,the comprehensive evaluation D values of the acid-aluminum tolerance of the 26 varieties were calculated based on the subordinate function values combined with the weights of the contribution rates of the two new comprehensive indexes.By clustering analysis on the D values,the 26 varieties were divided into 3 groups.Three varieties with the highest D values among the 26 varieties,Yunzhe 11-1074,Zhongtang 2 and Haizhe 28,were classified as varieties with strong aluminum tolerance,and 11 varieties including Yuegan 56 and Guitang 58,were moderately aluminum tolerant,while 12 varieties including Haizhe 32 and Yunrui 10-187 were sensitive to aluminum stress.Finally,the optimal regression equation analysis was carried out with the comprehensive evaluation D value of aluminum tolerance as the dependent variable and the aluminum toxicity tolerance coefficients of various indexes as independent variables,and the evaluation model of aluminum tolerance in sugarcane was established.Root length,root dry weight,relative chlorophyll content,leaf proline content,shoot aluminum content and root aluminum content,which had significant effects on aluminum tolerance of sugarcane seedlings,were selected as the evaluation indexes of acid-aluminum tolerance of sugarcane seedlings.[Conclusions]This study not only obtained a number of aluminum-tolerant varieties,but also provides a theoretical basis and reference for future genetic breeding of aluminum-tolerant sugarcane.