Evaluation system construction of physiological and biochemical indexes of low potassium tolerance of balsam pear

【Objective】The purpose of the study was to explore the identification of balsam pear germplasm resources that were resistant to low potassium stress，and to provide germplasm resources for cultivating high-yield and high-quality balsam pear varieties with low potassium tolerance.【Method】Eleven balsam pear germplasms were used as materials， and two treatments of low potassium（K⁺ concentration of 0.2 mmol/L）and normal potassium（K⁺ concentration of 4.0 mmol/L）were set up. The growth and physiological indexes of balsam pear germplasms under low potassium stress were comprehensively analyzed by multivariate statistical method. 【Result】The variation of 15 identification indexesof balsam pear germplasm，including plant height，stem diameter，internode length，leaf area，underground dry weight，above ground dry weight，root length，root surface area，root volume，chlorophyll a，chlorophyll b，carotenoid，total chlorophyll， malondialdehyde and potassium accumulation was large， with the coefficients of variation exceeding 10.0%. Principal component analysis was used to standardize the stress coefficients of 15 identification indexes （Z-score method） and reduce the dimensionality of the coefficients. From all the factors，the stress coefficients were focused into 4 principal components，which accounted for 83.690% of the total variation. According to the scores of the four principal components， the membership function values were calculated and comprehensive index（D value）was finally determined. The 11 germplasms were divided into four categories by cluster analysis method. The germplasms 04-25，1717，KG01-2 and 03-8 in class Ⅰwere low potassium tolerant，the germplasms 1721，11-8，DD14-1，04-17-4 and 26-2 in class II were medium low potassium tolerant，the germplasm 06-16 in class IIIwere low potassium weakly sensitive，and the germplasm 25-15 in class III were low potassium sensitive. The optimal comprehensive evaluation mathematical model was established by multiple regression analysis： Y=0.768×plant height+0.443×potassium accumulation+0.390×root surface area+0.595×chlorophyll a -0.415.【Conclusion】Among the 11 balsam pear germplasms，04-25 is the most lowpotassium tolerant germplasm. Plant height，potassium accumulation，root surface area and chlorophyll a can be used as the evaluation indexes for the low potassium tolerance of balsam pear germplasm. The evaluation system can be used for the rapid screening of the low potassium tolerance of balsam pear germplasm.