Effect of drought on morphological traits of fibre flax cultivars and breeding lines

Research aimed to stud y the effect of soil moisture deficit on the morphological traits of 12 fibre flax cultivars and breeding lines to identify drought-tolerant genotypes. Experiments were carried out in the Tver region (2023-2025) in a vegetation house using Mitscherlich pots: the control (optimal conditions) maintained soil moisture at 60-70% of full water capacity (FWC), while the experimental treatment (drought conditions) maintained it at 30-40% of FWC. Reduced soil moisture levels were maintained during the developmental period between the herringbone phase and budding, after which optimal moisture levels were restored. The experiment was set up with six replicates. In the drought treatment, the reduction in plant height compared to the control reached 40.0% at the budding stage (variety Levit 1), indicating the severity of the selective background. A comprehensive assessment showed that the genotypes Grant, Lira (Belarus), Hermes (France), and Merylin (the Netherlands), as well as the standard cultivar Atlant (Russia), showed only minor differences from the control regarding the morphological traits significant for breeding, indicating their drought tolerance. Notably, the accession v-51009 (China) was distinguished by superior productivity and fibre quality, demonstrating high plasticity under conditions of soil moisture deficit. These genotypes show promise as source material for breeding drought-tolerant fibre flax. Accessions v-8744-10 (China) and B-117 (Lithuania) proved to be the most sensitive to soil moisture deficit; compared to the control, their plant height decreased by 14.2 % and 21.7 %, technical stem length by 15.1 % and 19.7 %, fibre mass by 39.9 % and 56.7 %, fibre content by 2.7 % and 5.2 %, and elementary fibre length by 6.3 % and 13.3 %, respectively.