Simulating water deficit in cultivated flax (Linum usitatissimum L.)

Background: The reintroduction into cultivation of resilient, native, or historically cultivated species such as flax (Linum usitatissimum L.) represents an opportunity for sustainable agriculture, as these species demonstrate a higher capacity to adapt to water scarcity and unfavorable soil conditions, compared to agricultural systems based on intensive monocultures. Aim of the study: To evaluate the germination behavior of local flax forms (Linum usitatissimum L.) under water stress induced by PEG 6000, in order to identify genotypes with enhanced drought tolerance. Materials and methods: Two local flax (Linum usitatissimum L.) accessions from the Gene Bank's ex situ collection were used as study material: DRS-09 (Sofia vlg., Drochia dist.) and CSG-22 (Grigorievca vlg., Causeni dist.). To investigate plant responses to water stress, a polyethylene glycol 6000 (PEG 6000) solution was applied at five concentrations (0% - control, 10, 15, 20 and 25%) as a standard method for simulating drought conditions under controlled laboratory environments. The samples were exposed to a temperature of 20±1 for 6 days. Results: The results showed a clear variation in germination capacity and seedling growth depending on the intensity of osmotic stress induced by PEG 6000. Under non-stress conditions (0% PEG), the genotypes exhibited high germination rates, 90% for DRS-09 and 88% for CSG22. At 10% PEG, a slight stimulation of germination was observed, with both genotypes reaching values of up to 94%. As the concentration increased to 15% and 20% PEG, germination remained relatively stable, ranging between 88-92% and 86-88%, respectively, while at 25% PEG germination was completely inhibited (0%). In the absence of osmotic stress, the DRS-09 genotype exhibited superior vigor, with an average seedling length of 15.67±0.60 cm compared to 9.96±0.57 cm for CSG-22. PEG application resulted in a progressive reduction in growth, which became more pronounced with increasing stress intensity. At 10% PEG, seedling length was 11.40±0.65 cm (DRS-09) and 9.02±0.53 cm (CSG-22), followed by marked decreases at 15% PEG (6.82±0.40 cm and 4.26±0.26 cm). At 20% PEG, growth was severely inhibited, reaching values of 1.75±0.07 cm and 1.67±0.09 cm and at 25% PEG, complete suppression of germination and growth was observed. Overall, the results indicate increased sensitivity to severe stress and differential tolerance among genotypes under moderate stress conditions. Conclusions: The DRS-09 genotype showed higher overall tolerance to PEG-induced water deficit and represents the most promising material for further study. A PEG concentration of up to 20% is recommended for future screening of flax genotypes, as it effectively differentiates stress responses.