Toxicity indicators and biochemical responses in leaves of 'Tahiti' acid lime grafted on ten Citrus rootstocks under salt stress

Searching for salt tolerant genotypes is a strategy to reduce the impacts of salinity on agriculture sustainability. For grafting-propagated species as Citrus, evaluating scion/rootstock combinations could be critical for searching salt tolerant genotypes as mutual influences can occur. Here we evaluated plant growth (stem diameter measured at the rootstock-grafting point), ionic toxicity indicators (Cl-, Na+, and Na+/K+ ratio), biochemical and nutritional responses (activities of ascorbate peroxidase-APx and superoxide dismutase-SOD, concentration of organic solutes, N and K) in leaves of 'Tahiti' acid lime (Citrus latifolia) grafted on ten Citrus rootstocks under irrigation with saline water. The study was carried out under semi-arid conditions testing two levels of electrical conductivity in the irrigation water (0.3 and 3.0 dS m(-1)) and ten scion/rootstock combinations evaluated on the spring of different years (Nov 2016 and 2017). Significant correlations between ionic toxicity indicators and biochemical responses were more associated with salinity exposure time than with different genotypes (scion/rootstock combinations). The ionic toxicity indicators, especially Cl- concentration, enabled more accurate genotypic screening for selection of salt-tolerance when compared to biochemical responses. The hybrid TSKC x (LCR x TR) 017 (Cross between common 'Sunki' mandarin x ('Rangpur' lime x Poncirus trifoliata) was the most promising salt-tolerant rootstock because it grew more and showed low ionic toxicity.