<i>In vitro</i> study of the effect of NaCl on interspecific <i>Populus</i> L. hybrids

In conditions of climate aridisation and desertification of territories leading to secondary soil salinisation, more and more lands are subjected to premature degradation and their further withdrawal from agricultural use. In vitro modelling of stress factors for selection of tolerant lines of salt-tolerant genotypes of tree species helps to accelerate the breeding process. In the study, the effect of NaCl on morphogenesis of regenerant plants of poplar F1 interspecific hybrids (Populus L.) was investigated, and in vitro selection of potentially co-tolerant genotypes was carried out. After controlled crossing of selected parental lines with economically useful traits (Populus deltoides × P. alba; P. nigra f. piramidalis × P. alba; P. deltoides × P. bolleana f. piramidalis) by the method of isolated embryos, aseptic explants of interspecific hybrids were obtained and micropropagated. Sixteen genotypes of 10 clones each were tested on selective media with NaCl at concentrations of 0.2; 0.5;1.0 % in three replicates. The ratio of surviving and regenerating explants, the frequency of rhizogenesis and the percentage of chlorosis among the tested accessions, as well as shoot length and number, multiplication factor and number of nodes were determined.  The inhibitory effect of salt stress was manifested in the inhibition of morphogenesis, including the absence of rhizogenesis processes, chlorosis, partial deformation and necrosis of leaf plates. A dose of 0.5 % NaCl was determined to be sublethal and 1 % was lethal. Among the sixteen genotypes tested, 4 genotypes had high % of surviving explants (96.2–96.7 %), two of which maintained high % regeneration (82.6–96.6 %) at sublethal concentration of selective agent. These results suggest that in vitro testing for NaCl tolerance is a promising tool for accelerating the breeding process and selecting potentially tolerant genotypes to the abiotic stress factor for further field trials.