In vitro modelling of salinity stress for the selection of stress-tolerant birch lines

Abstract

This paper examines the salinity stress effect in vitro culture of microshoots of 10 birch clones: Betula pendula L., B. pendula Roth var. carelica (Mercklin) Hämet-Ahti, B. pendula f. ’dalecarlica’ (L.f.) Schneid., B. pubescens Ehrh. We used economically valuable and genetically diverse (various species, varieties, hybrids, polyploids) birch material from in vitro clone collection. We tested 3 in vitro selection methods on 1/2 MS hormone-free nutrient medium: mild – with a prolonged exposure to 0.2% NaCl; gradual – with a step-by-step increase in osmotic concentration (from 0.2% to 1%); severe – with a sublethal (1%) NaCl concentration. We established that the gradual method of NaCl exposure according to the following pattern: 0.2% → 0% → 0.5% → 0% → 0.75% → 0% → 1.0% resulted in the best selective effect for birch, as it provides a clear differentiation of clones in terms of their salinity tolerance. We identified that the genotype had a significant impact on the preservation of the explants and their ability to regenerate under salinity stress. The study showed that tetraploid clones of downy birch and a triploid clone of Karelian birch of a pronounced mixoploid nature had the greatest salinity tolerance.