Sunflower grain yield and oil content affected by zinc fertilization and genotype in drought stress conditions

Context: Drought stress is a major environmental factor limiting sunflower (Helianthus annus L.) growth and productivity, worldwide. Although there has been research on the use of zinc (Zn) to alleviate drought stress in sunflower, more has yet to be indicated on how Zn may affect sunflower yield and biochemical properties in drought stress conditions as the objective of the present research. Methods: The field experiment was a split plot on the basis of a complete randomized block design with 18 treatments and 3 replicates conducted in the province of Fars, Iran, in 2018. The experimental treatments of drought (main plots) including irrigating at 70 (control, S1), 105 (mild, S2) and 140 mm (severe, S3) evaporation from the evaporation pan and the sub plots (factorial arrangement) of sunflower genotypes (Shams and Barzegar) and Zn fertilizer (ZnSO4) at 0, 40 and 70 kgha−1 were tested. Different sunflower, growth, yield and biochemical parameters were determined. Results: Stress significantly affected leaf area index (LAI), tray diameter (TD), grain weight (GW), infertile seeds (I), water use efficiency (WUE) and proline (Pr), and genotype was significant on LAI, TD, number of grains per tray (NGT), GW, WUE, and grain protein (PP). However, Zn significantly increased LAI, PP, GW and WUE by 50, 5.9, 35 and 32 %, respectively. Conclusion: Zn fertilization can alleviate the unfavourable effects of drought stress on sunflower yield and biochemical properties by improving plant growth (LAI), yield (grain weight), and physiology (water use efficiency and protein percentage), and genotype is a determining factor.