Comprehensive evaluation and screening of salt tolerance for Leuce clones at nursery stage

Ten white poplar clones were used as the materials in this study to analyse the changes of growth and physiological indexes under different salt stresses (0, 0.1%, 0.3%, 0.5% and 0.7% NaCl concentration). The results showed that the height growth rate and the basal diameter growth rate of ten white poplar clones were inhibited apparently under high salt stress (P < 0.05). Clone 0057 showed fast-growing performance and high survival rate. The effects of low salt stress on the growth and cell membrane system of clones were not obvious, but it could induce the increase of antioxidant enzyme (SOD and POD) activity and soluble protein content. With the increase of NaCl concentration and the extension of salt treatment time, the protective enzyme activity, soluble protein content, cell membrane permeability and MDA content were significantly increased compared with the control. The salt tolerance coefficients of POD and soluble protein in ten clones were positively correlated with SOD, and the salt tolerance coefficient between POD and MDA was negatively correlated. The results showed that clones could reduce the accumulation of MDA and improve their salt tolerance by accumulating a large amount of soluble protein and enhancing the activity of antioxidant enzymes. Based on the principal component analysis and membership function analysis, the salt tolerance of ten clones was evaluated comprehensively. It is preliminarily considered that clones 0057, 422 and XJY have significant salt tolerance and fast-growing performance, which could be used as the important materials for afforestation in saline soil and breeding resource in resistance research.