Comprehensive evaluation of waterlogging tolerance of eleven Canna cultivars at flowering stage

Abstract

To identify and screen the waterlogging-tolerant cultivars of Canna spp. and establish a comprehensive, mathematical evaluation model of Canna plants, morphological characteristics and physiological indices were recorded and measured using the leaves of 11 cultivars. Their waterlogging tolerance was overall evaluated by calculating the waterlogging injury index (WII) and waterlogging tolerance coefficient (WTC) based on the morphological traits and physiological indices. Results revealed that after waterlogging stress, adventitious roots appeared in all cultivars, whose length and number increased as the stress persisted. Among the tested species, there were more adventitious roots observed in C. edulis Ker, C. waracewiezii Dietr. and C. orchioides Bailey., while C. indica L., C. flaccida Salisb., and C. generalis Bailey. had few adventitious roots. Additionally, the edges of the lower leaves of C. edulis Ker. cv. ‘PLRF’, ‘Xingyu-1′, ‘Xingyu-2′ and C. orchioides Bailey. cv. ‘Sajin’ yellowed the most and experienced the worst scorch. Damage was less obvious on C. generalis Bailey. cv. ‘Mohong’ leaves after waterlogging stress for 21 d Furthermore, ‘Mohong’ was determined to be the most waterlogging tolerant cultivar and had the lowest WII value (0.400), while the ‘PLRF’ had the highest (0.840) and clustered into the waterlogging-sensitive group. Four physiological indices, including catalase (CAT), peroxidase (POD), soluble sugar (SS) and malonaldehyde (MDA) increased (WTC > 1) after waterlogging, while soluble protein (SP) decreased (WTC < 1) in all cultivars. Changes in the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) differed among cultivars. Principal component analysis (PCA) transformed the 7 physiological indices into 4 independent, comprehensive indices, whose cumulative contribution ratio reached 96.062%. The 11 cultivars were divided into 4 categories based on the comprehensive evaluation value (D). ‘Mohong’, in the waterlogging-tolerant group had the highest D value (0.912). C. waracewiezii Dietr. cv. ‘Ziye Xiaojuhong’, C. generalis Bailey. cv. ‘Grand Due’, C. orchioides Bailey. cv. ‘Suihua Chenghong’ and C. indica L. belonged to the intermediate waterlogging-tolerant group with D values of 0.652, 0.616, 0.590 and 0.533, respectively. C. orchioides Bailey. cv. ‘Lüyecheng’, C. flaccida Salisb. cv. ‘Yellow Canna’, ‘Xingyu-1′ and ‘Xingyu-2′ were clustered into the low waterlogging-tolerant group with the D values of 0.458, 0.455, 0.421 and 0.368, respectively. Lastly, ‘Sajin’ and ‘PLRF’ clustered into the sensitive waterlogging tolerant group with the lowest D value of 0.201 and 0.170, respectively. The stepwise regression analysis showed that CAT, POD, SOD, APX, SS and MDA, can be used to evaluate and predict the waterlogging tolerance of different Canna lily cultivars.