Bio-Fertilizers and Zinc Sprays Boost Drought Tolerance in Black Cumin

A newly published study in Acta Physiologiae Plantarum reveals that combining arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PB2), and zinc foliar applications significantly enhances drought tolerance in black cumin (Nigella sativa). Conducted over two years in Iran, the research examined how beneficial microbes and zinc supplementation can mitigate physiological damage caused by reduced irrigation.

Black cumin is widely cultivated in dry and semi-arid regions but remains sensitive to water stress—especially during grain formation. The study reports that drought conditions drastically decreased photosynthetic pigments, relative water content, soluble proteins, and yields, while increasing electrolyte leakage, proline, and soluble sugars.

Microbial Bio-Fertilizers Improve Plant Nutrient Status Under Drought

The study demonstrates that applying AMF along with PB2 (which contains Pseudomonas putida P13 and Pantoea agglomerans P5) significantly increased grain nitrogen, phosphorus, and zinc content. The combined microbial treatment also reduced electrolyte leakage and supported higher photosynthetic pigment levels, even under 50% irrigation.

Zinc Spray Enhances Photosynthesis and Stress Tolerance

Applying zinc sulfate (3 g/L) improved chlorophyll content, soluble sugars, proline, relative water content, and membrane stability. Zinc-treated plants showed reduced drought-induced damage across physiological indicators.

Yield Improvements Despite Water Shortage

Under both full and reduced irrigation, the AMF + PB2 combination consistently produced the highest biological performance and grain yield. Even under severe drought, grain yield increased by up to 46% with bio-fertilizer application compared to untreated plants.

A Promising Strategy for Climate-Resilient Agriculture

The study concludes that integrating AMF, phosphate-solubilizing bacteria, and zinc foliar sprays offers a powerful, eco-friendly approach to enhance drought tolerance and productivity in black cumin. This strategy could be valuable for sustainable agriculture in arid and semi-arid regions, where water scarcity threatens crop health and yield.

Reference

Rafiee, S., Yadavi, A., Dehnavi, M.M. et al. Arbuscular mycorrhizal fungi, phosphate-solubilizing bacteria, and zinc foliar application improve physiological responses in black cumin (Nigella sativa) under drought stress. Acta Physiol Plant 47, 114 (2025). https://doi.org/10.1007/s11738-025-03856-8