Zinc Biofortification of Microgreens Using Different Agronomic Approaches
Open Access
- Author:
- Poudel, Pradip
- Graduate Program:
- Agricultural and Environmental Plant Science (PhD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 18, 2025
- Committee Members:
- Misha Kwasniewski, Outside Unit Member
Erin Connolly, Major Field Member
Francesco Di Gioia, Chair & Dissertation Advisor
Joshua Lambert, Outside Field Member
Erin Connolly, Program Head/Chair - Keywords:
- Hidden hunger
Agronomic biofortification
Seed nutri-priming
Zinc deficiency
Nutritional quality
Metabolomics - Abstract:
- Micronutrient deficiencies, including zinc (Zn), are a growing global health concern, exacerbated by climate change, the Covid-19 pandemic, and political conflicts in different regions. Agronomic biofortification of crops, especially nutrient-dense microgreens, offers a potential solution to mitigate this issue. Microgreens, with their short growth cycles and high nutrient content, present an ideal target crop for Zn biofortification through agronomic approaches like seed nutri-priming and fertigation. A series of studies were conducted to explore the potential of Zn biofortification in pea, radish, and sunflower microgreens using different Zn sources (ZnSO4, nano-ZnO, and Zn-EDTA), application methods (seed soaking and fertigation), rates (0, 25, 50, 100, 200 mg/L and 0, 5, 10, 15 mg/L for seed nutri-priming and fertigation, respectively) and light intensity level (100, 200, 300 and 400 μM/m2/s PPFD). Impact on Zn content and bioaccessibility, yield, and quality components were examined. Further, a comprehensive analysis of the metabolomic profile of pea and radish microgreens was done to assess how Zn application rate and light intensity affect the content of specific phytonutrients and bioactive compounds employing a targeted metabolomics approach using LC-MS/MS. Results demonstrated that ZnSO4 was the most effective source for increasing Zn content across all species using both application approaches tested. Pea and sunflower microgreens biofortified through seed soaking resulted in 1.3- and 2.3-fold increases in Zn concentration, respectively. Fertigation with 15 mg/L ZnSO4 increased Zn content by factors of 5, 13, and 6 in pea, radish, and sunflower microgreens. A follow-up study focused on ZnSO4 fertigation under varying light intensity levels demonstrated a significant increase in Zn content and an enhanced Zn bioaccessible fraction; 4-fold in peas and 17-fold in radish compared to the control (0 mg/L Zn). While Zn biofortification improved the nutritional profile of all microgreen species by enhancing the content of phytochemicals (total phenolics, flavonoids, and antioxidant activity), it also reduced other essential microminerals like iron (Fe). Light intensity did not affect Zn content, but increased the content of phytochemicals, enhancing the overall nutritional profile of microgreens. Further, the metabolomic analysis revealed that light intensity and Zn application rate independently modulated the metabolic profile of pea and radish microgreens. In peas, high light intensified oxidative stress responses, phenylalanine reallocation, and carbohydrate metabolism. Zn application specifically increased sulfur-containing amino acids and branched-chain amino acids, aiding detoxification and antioxidant defense. In radish, high light intensity promoted stress resilience through flavonoid and phenolic acid accumulation while modulating nitrogen and energy metabolism under Zn stress. This study underscores the potential of microgreen Zn biofortification via seed nutri-priming and fertigation to combat Zn deficiency, with careful optimization of Zn source, application rate, and light conditions. These findings offer valuable insights into enhancing the nutritional and functional quality of microgreens, contributing to global nutrient security and the growing demand for functional food.