Formulation of zinc foliar sprays for wheat grain biofortification: a review of current applications and future perspectives

Abstract

Agronomic biofortification of wheat grain with zinc can improve the condition of about one billion people suffering from zinc (Zn) deficiency. However, with the challenge of cultivating high-yielding wheat varieties in Zn-deficient soils and the global need to produce higher-quality food that nourishes the growing population, innovation in the strategies to deliver Zn directly to plants will come into play. Consequently, existing foliar formulations will need further refinement to maintain the high agronomic productivity required in competitive global grain markets while meeting the dietary Zn intake levels recommended for humans. A new generation of foliar fertilisers that increase the amount of Zn assimilated in wheat plants and the translocation efficiency of Zn from leaves to grains can be a promising solution. Research on the efficacy of adjuvants and emerging nano-transporters relative to conventional Zn forms applied as foliar fertilisers to wheat has expanded rapidly in recent years. This review scopes the range of evidence available in the literature regarding the biofortification of bread wheat (Triticum aestivum L.) resulting from foliar applications of conventional Zn forms, Zn nanoparticles and novel Zn-foliar formulations. We examine the foliar application strategies and the attained final concentration of grain Zn. We propose a conceptual model for the response of grain Zn biofortification of wheat to foliar Zn application rates. This review discusses some physiological aspects of transportation of foliarly applied Zn that need further investigation. Finally, we explore the prospects of engineering foliar nano-formulations that could effectively overcome the physicochemical barrier to delivering Zn to wheat grains.

Application of Zinc Oxide Nanoparticles to Mitigate Cadmium Toxicity: Mechanisms and Future Prospects

“…In foliar spray, ZnO-NPs are applied to the leaf surface and then they are absorbed by leaf cuticle and stomata. As a result, nanoparticles are transported within the plants through phloem sieve tubes [ 62 ]. For instance, Zhu et al [ 63 ] reported that ZnO-NPs penetrate the leaf epidermis through stomata, accumulate in the plastid, and translocate into chloroplasts.…”

Synthesis of Zinc Oxide Nanoparticles and Their Applications in Enhancing Plant Stress Resistance: A Review

“…In the case of foliar application, ZnO nanoparticles are sprayed onto the leaf surface and can be absorbed through the stomata and cuticle (Figure 2A). Subsequently, they are further transported within the plant through phloem sieve tubes, facilitating their wholeplant conduction [125]. Zhu et al demonstrated that ZnO nanoparticles can penetrate the epidermis through stomata, accumulate in plastid exosomes, and then translocate to chloroplasts [65].…”

Influence of Fertilization Methods and Types on Wheat Rhizosphere Microbiome Community and Functions

“…In addition to being a major source of starch and energy, it also provides proteins, vitamins, dietary fibers, and phytochemicals . The yield and quality of wheat are greatly dependent on chemical fertilizers, and nitrogen (N) and potassium (K) play an important role in improving the wheat yield and quality. − As an essential micronutrient, zinc (Zn) application in wheat, especially foliar spraying, effectively alleviates zinc deficiency in humans. − However, current agricultural practices have focused on the long-term application of chemical fertilizers, which while effective has also created problems in the soil environment. Improving wheat yield by changing the plant microbiome to improve its nutrient uptake and resistance to pathogens is of great significance for the sustainable development of an intensive agricultural ecosystem. − …”