Seed coating with minerals and plant growth-promoting bacteria enhances drought tolerance in fennel (Foeniculum vulgare L.)

The seeds of many plants, including fennel (Foeniculum vulgare L.), are tiny and have low food reserves. Therefore, planting them accurately in the soil to achieve optimal yields is challenging. The present research aimed to study the impact of bio-priming and seed coating on seedling and vegetative growth of fennel plants under drought stress. The experiments were conducted in laboratory and greenhouse conditions triplicate using a completely randomized design (CRD). These experiments applied mineral and biological coating treatments as the first factor and drought tolerance at three levels (0, −0.3, and −0.6 MPa) as the second factor. Perlite (P), Vermiculite (V), and Kaolin (K) were used as a mineral coating. The mineral coating mixture was P10V10K5. The numbers mean the material (gr) ratio based on the seed weight. Combinational treatments of seed coating were CHA0 + coating, PF56 + coating, T39 + coating, T36 + coating, and non-coating (as control). Pseudomonas fluorescens P.F56, P. fluorescens CHA0, and Trichoderma harzianum T36 and T. harzianum T39 were employed as biological treatments. Experimental results showed that at 0 and -0.3 MPa osmotic potential levels, the T39 + coated seeds had the highest percentage of seedling emergences. At the −0.3 MPa level, the T39 + coated seeds had an increased seedling emergence percentage by 24% compared to un-inoculated seeds. At all levels of drought stress, the CHA0 + coated treatment had the highest level of chlorophyll a content, CAT, and APX enzyme activity. Seed coating with CHA0 and T39 enhanced fennel's early vegetative growth and biochemical characteristics under normal and drought stress and mitigated drought stress. •Bio-priming with minerals and rhizobacteria promoted seedling and vegetative growth of fennel under drought stress.•Pseudomonas CHA0 coated treatment yielded the highest chlorophyll and antioxidant enzymes under drought stress.•Seed coating with rhizobacteria enhanced early seed germination under normal and drought stress.