Multivariate analyses discern shared and contrasting eco-physiological responses to salinity stress of Ziziphus rootstocks and budded trees

Abstract

This study aimed at delineating the eco-physiological responses to salinity stress of three Ziziphus rootstocks [Z. rotundifolia (ZR), Z. spina-christi (ZS), Z. mauritiana cv. Tikadi (ZMT)] and Indian jujube cv. ‘Gola’ budded on them. The repressive effects of saline irrigation (ECiw ∼6.0 dS m−1) on vegetative growth compared to the best available water (∼ 3.0 dS m−1) irrigated controls were more pronounced in ZMT and ZS than in ZR, reflecting strong rootstock-specific responses to salt stress (p <0.001). Likewise, salt-stressed ‘Gola’ scions on different rootstocks showed varying reductions in trunk and canopy growth. While leaf relative water content decreased, malondialdehyde (MDA) increased in both rootstocks and budded trees receiving 6.0 dS m−1 water (p <0.001). However, ZR/ZS seedlings and ‘Gola’ scions on them were relatively less affected by MDA-induced oxidative stress. Despite a significant salt-induced increase, leaf proline levels seemed to be rather low to elicit salt stress response in both rootstocks and budded trees. ZR plants, with or without ‘Gola’ scions, were more efficient in Na+ and Cl− exclusion than both ZS and ZMT. In contrast to rootstock plants in which excess Na+ had a major growth limiting effect, MDA and Na+were equally deleterious to canopy expansion while Cl− alone to trunk growth in the budded trees. Principal Component Analysis clearly explained rootstock- and salinity-specific effects in data. Multidimensional scaling revealed that elevated Na+ was the key trigger to MDA accumulation in rootstock and budded tree leaves. Based on network analysis, MDA and Cl- were found to be the key traits underpinning salt stress response in rootstock plants, and Cl−, MDA and K+ in the budded trees.