Characterization of physiological responses and fatty acid compositions of Camelina sativa genotypes under water deficit stress and symbiosis with Micrococcus yunnanensis

The effects of drought on growth and seed quality of oilseed crops are of crucial importance in edible oil production due to its pivotal role in sustainable agriculture. Plant growth-promoting bacteria (PGPB) can improve crop yield by promoting plant growth under various environmental conditions. In the present study, the physiological responses, growth, and seed quality of three camelina doubled haploid lines (DH51, DH69, and DH104) were assessed upon their exposure to two irrigation regimes at the presence of Micrococcus yunnanensis during their reproductive phase. The results showed that the investigated parameters of camelina were affected by genotype, irrigation regimes, and PGPB. Drought decreased crop yield as measured by silique length, silique, and seed number and 1000-weight seed. PGPB significantly decreased the adverse effects of stress consistent by increasing the branches per plant and root length. Drought also caused a significant enhancement in the hydrogen peroxide and malondialdehyde contents, but the PGPB-inoculated plants showed lower contents of both compounds. Relative water content significantly reduced in plant grown under stress but inoculation enhanced the potential of water retaining in plants under stress and non-stress conditions. Drought stress and PGPB elevated proline and total soluble carbohydrate content in genotypes. Drought stress had no significant effect on photosynthetic pigments content of genotypes while inoculation apparently moderated negative impact of drought with enhancement of pigments content. The obtained results were responsible for metabolic changes occurring in response to stress. PGPB improved the plant drought-tolerance by enhancing its physiological traits. The fatty acid profile showed some variations among camelina genotypes under drought stress and PGPB inoculation. Upon symbiosis association, an increase was observed in major constituents of polyunsaturated acids, linoleic and linolenic acids, and a significant increase in oleic acid as a main monounsaturated acid. They also altered another major constituent, gadeolic acid, under water deficit stress and/ or with PGPB. Both drought stress and PGPB decreased the poly unsaturated fatty acids/mono unsaturated fatty acids ratio. In general, there was a significant difference among camelina lines in terms of seed yield and quality in response to drought. Also, it strongly suggested that PGPB application can be a positive strategy to mitigate drought stress and increase crop yield.