Investigation of salinity tolerance to different cultivars of highbush blueberry (Vaccinium corymbosum L.) grown in vitro

Abstract

Salinity is one of the most critical abiotic stresses affecting various physiological, biochemical, and molecular functions of plants. This study aimed to assess the effects of different salt concentrations on in vitro blueberry shoots (‘Bluecrop’, ‘Blueray’, ‘Brigitta Blue’, ‘Duke’, ‘Goldtraube’, ‘Hortblue Petite’, and ‘Patriot’ cultivars) and to understand the mechanisms employed by this species under saline conditions. The Woody Plant Medium (WPM) proliferation medium was supplemented with 10, 50, 100, and 150 mM NaCl to induce salt stress. After ten weeks of in vitro culture under salinity stress, various parameters were evaluated, including the number of shoots obtained/explant, shoot length, fresh weight, dry weight, water content, stress tolerance index (STI), and McKinney index (MKI). Additionally, the behaviour of blueberry cultivars under salt stress was analyzed using electron paramagnetic resonance spectroscopy (EPR). Compared to the control (culture medium without NaCl), all treatments with NaCl reduced shoot length and the number of shoots obtained/explant in all studied blueberry cultivars. ‘Brigitta Blue’ reported the shortest shoots (0.04 ± 0.02 cm) at a concentration of 150 mM NaCl, followed by ‘Blueray’ with 0.05 ± 0.03 cm. Also, the lowest number of shoots/explant was recorded for both cultivars under 150 mM NaCl, namely 0.12 ± 0.07 shoots/explant (‘Brigitta Blue’) and 0.11 ± 0.04 shoots/explant (‘Blueray’). Salt tolerance, as expressed by ITS and MKI, confirmed that ‘Goldtraube’ exhibited higher salt tolerance, with the highest ITS values and the lowest MKI values. Further validation presented ‘Goldtraube’ as the most unresolved spectra of the Mn (II) hyperfine structure under all salt concentrations, therefore ‘Goldtraube’ was the most tolerant to saline stress.