In 2025, a groundbreaking study published in the Journal of Plant Growth Regulation revealed a powerful solution to a common problem in grape farming: magnesium deficiency.

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Researchers from the Sichuan Academy of Agricultural Sciences discovered that two plant growth regulators (PGRs)—6-Benzylaminopurine (6-BA) and 28-Homobrassinolide (HBL) can significantly improve magnesium absorption in Vitis vinifera cv.

Shine-Muscat grapes while boosting fruit quality. Magnesium is vital for photosynthesis and energy production in plants, but its deficiency often leads to yellowing leaves, delayed ripening, and poor yields. By combining these PGRs with magnesium fertilizers, farmers can address these challenges effectively.

Understanding Magnesium Deficiency in Grapes

Magnesium plays a central role in plant health. It forms the core of chlorophyll, the green pigment essential for photosynthesis, and activates enzymes involved in energy transfer. However, modern farming practices, such as excessive use of potassium or calcium fertilizers, often disrupt magnesium uptake.

This leads to magnesium deficiency, marked by yellowing between leaf veins (chlorosis), stunted growth, and reduced fruit sugar content. For premium table grapes like Shine-Muscat—known for their crisp texture and sweet flavor—this deficiency can cause significant economic losses.

To tackle this issue, the research team explored how PGRs, which are natural or synthetic compounds that regulate plant growth, could enhance magnesium absorption. Specifically, they tested 6-BA (a cytokinin that promotes cell division) and HBL (a brassinosteroid that improves stress tolerance).

How the Study Was Conducted

The researchers designed two experiments: controlled pot trials and real-world field tests.In the pot experiments, Shine-Muscat grapevines were grown under two conditions: magnesium-deficient soil (to mimic common farming challenges) and normal soil.

The plants were treated with either magnesium fertilizer (MgSO₄) alone, 6-BA or HBL alone, or a combination of magnesium and PGRs.After 11 days, the team measured magnesium levels in leaves, stems, and roots.

They also used RNA sequencing, a technique to analyze gene activity, to identify 15,549 genes that responded to magnesium deficiency. Key genes involved in chlorophyll production (CHLH, CAO) and stress response (ERF1, CKX3) were closely monitored.

Key Findings: PGRs Boost Magnesium Uptake and Fruit Quality

The results were striking. In the pot experiments, combining magnesium fertilizer with HBL increased magnesium levels in leaves by 23%, from 0.207% in untreated plants to 0.254%. Similarly, 6-BA raised leaf magnesium by 12%.

The PGRs redirected magnesium from roots and stems to leaves, where it’s most needed for photosynthesis. For example, root magnesium content dropped from 0.183% to 0.146% with HBL alone, while leaf levels rose.

In the field trials, 6-BA and HBL alone increased leaf magnesium by 65% and 91%, respectively, compared to untreated vines.

When paired with magnesium fertilizer, the PGRs improved magnesium absorption efficiency by 18–32%.This synergy not only resolved nutrient deficiencies but also enhanced fruit quality. Grapes treated with HBL and magnesium, for instance, weighed 24% more (19.36g vs. 15.53g) and had 62% higher vitamin C levels.

Improved Fruit Quality: Sweeter, Larger, and More Aromatic Grapes

Beyond resolving magnesium deficiency, the PGRs transformed fruit quality. Grapes treated with 6-BA alone had 114% more sugar (1.89 mg/g vs. 0.88 mg/g in controls), while HBL boosted vitamin C by 62%.

Tartaric acid, the primary sour component, decreased from 81.2% to 78.2% when HBL was paired with magnesium, making the fruit taste sweeter.Aroma analysis revealed even more benefits. 6-BA combined with magnesium increased esters and benzenes.

HBL alone elevated terpenoids aroma molecules linked to citrus and herbal scents to 94.8% of total volatile compounds. These changes align with consumer preferences for complex, appealing flavors in premium table grapes.

Why These Results Matter for Farmers

For grape growers, these findings offer three key advantages. First, higher profits from larger, sweeter, and more aromatic grapes that meet premium market demands. Second, reduced fertilizer waste, as PGRs enhance magnesium absorption efficiency, lowering costs and environmental impact.

Third, healthier vines, as delayed leaf aging supports photosynthesis over multiple growing seasons.However, the study noted challenges. Younger vines responded better to PGRs than older ones, emphasizing the need for early intervention.

Additionally, while PGRs enhanced fruity and floral aromas, they reduced green scents like leaf alcohol, which might affect flavor complexity for some consumers.

Practical Steps for Growers

To implement these findings, farmers should:

Apply PGRs early: Target the fruit-softening stage (July in the study) for maximum impact.
Combine PGRs with magnesium fertilizers: This pairing boosts nutrient uptake efficiency.
Test soil regularly: Monitor magnesium levels to avoid over-fertilization and maintain soil health.

Future Research and Sustainability

While the study focused on short-term results, long-term effects on soil microbes and PGR residues require further exploration. Future research could also optimize PGR concentrations (beyond 20 ppm for 6-BA or 0.04 ppm for HBL) and test these methods on other magnesium-sensitive crops like tomatoes or citrus.

Conclusion

This research bridges science and practical farming, proving that plant growth regulators like 6-BA and HBL can resolve magnesium deficiency, boost yields, and enhance fruit quality. For growers struggling with yellowing leaves or poor harvests, these PGRs offer a simple yet powerful tool.

Smart nutrient management isn’t just about quantity it’s about synergy. PGRs unlock magnesium’s full potential, turning challenges into opportunities. By adopting these strategies, farmers can cultivate healthier vines, tastier grapes, and sustainable profits for years to come.

Reference:

Wang, Q., Yang, Y., Wang, H. et al. Effects of Plant Growth Regulators on Magnesium Absorption and Fruit Quality in “Vitis vinifera cv. Shine-Muscat” Grape. J Plant Growth Regul (2025). https://doi.org/10.1007/s00344-025-11678-8

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