Seed Derived Bacterial Bioformulation Improves Peanut Growth and Fungal Defense

Peanuts (Arachis hypogaea L.) are one of the world’s most vital crops, providing oil, protein, and essential nutrients to millions of people, particularly in tropical and subtropical regions. Despite their importance, peanut farmers face a relentless challenge soilborne fungal diseases—infections caused by fungi that live in the soil and attack plant roots, stems, or pods.

These diseases, caused by pathogens like Sclerotium bataticola (which causes charcoal rot, a condition where plants wilt and stems turn black) and Fusarium solani, can devastate entire fields, leading to massive economic losses and food shortages. Traditional solutions, such as chemical fungicides (synthetic chemicals designed to kill fungi), often harm the environment and become less effective as fungi develop resistance.

In 2025, a team of international researchers published a groundbreaking study in the European Journal of Plant Pathology that offers a sustainable alternative—a bioformulation containing Serratia proteamaculans Sp77, a beneficial bacterium found inside peanut seeds.

This discovery has the potential to transform agriculture by combining disease control, improved crop yields, and enhanced nutritional value, all without relying on harmful chemicals.

The Global Threat of Soilborne Fungal Diseases

The threat posed by soilborne fungi to peanut crops cannot be overstated. For example, Sclerotium bataticola thrives in warm, dry soils and can cause yield losses of 30–50% during droughts.

This fungus produces sclerotia (hard, dormant structures) that survive in soil for years, making it difficult to eradicate. Similarly, Fusarium solani attacks peanut pods, often going undetected until harvest, and reduces both quality and yield by 20–40%.

In Egypt, where peanuts are grown across 90,000 hectares, these diseases cost farmers millions of dollars annually.

Chemical fungicides like Rhizolex-T 50% WP (a common fungicide containing tolclofos-methyl) have been widely used, but they come with significant drawbacks.

Not only are they expensive—costing up to $50 per hectare—but they also contribute to environmental pollution and can lead to pathogen resistance (when fungi evolve to survive chemical treatments) over time.

To address these challenges, researchers turned to a promising natural solution: endophytic bacteria—microbes that live inside plant tissues without causing harm and can protect crops from disease while promoting growth.

Discovering Serratia proteamaculans Sp77 Dual-Action Bacterium

The study began with a simple yet ambitious goal: to identify endophytic bacteria within peanut seeds that could combat fungal pathogens and enhance plant health.

After collecting peanut samples from seven regions across Egypt, the team isolated 38 bacterial strains (distinct types of bacteria). Among these, one strain stood out Serratia proteamaculans Sp77.

This bacterium demonstrated remarkable antifungal activity (ability to inhibit fungal growth), reducing the growth of Sclerotium bataticola by 41% and Fusarium solani by 45% in laboratory tests.

Further analysis revealed that Sp77 produced high levels of indole-3-acetic acid (IAA)—a plant hormone that stimulates root growth—as well as enzymes like protease (an enzyme that breaks down proteins) and chitinase.

These traits made Sp77 an ideal candidate for developing a bioformulation that could protect peanuts while boosting their productivity.

Developing the Bioformulation (BBF) Science Meets Practicality

To turn this discovery into a practical farming tool, the researchers developed a granular bioformulation (BBF)—a dry, pellet-like product containing live bacteria.

The process began by fermenting (growing in a nutrient-rich liquid) the bacteria in nutrient broth, then mixing the culture with natural ingredients like semolina flour, kaolin clay (a type of soft clay), and yeast extract (a nutrient source) to create a dough.

This dough was dried and ground into tiny granules, each measuring 1–1.2 millimeters—a size ideal for easy application in fields. The granules served as a protective carrier for the bacteria, ensuring they survived in the soil long enough to colonize peanut roots and deliver their benefits.

This formulation not only preserved the bacteria’s viability (ability to stay alive) but also made it cost-effective, with production costs estimated at $20 per hectare, less than half the price of traditional fungicides.

Greenhouse Trials Proving Efficacy Under Controlled Conditions

The next step was to test the BBF’s effectiveness in controlled greenhouse experiments. Peanut plants were grown in pots infected with Sclerotium bataticola or Fusarium solani, and different concentrations of BBF (1%, 1.5%, and 2%) were applied to the soil.

The results were striking. In pots treated with 2% BBF, seedling mortality (death of young plants) caused by Fusarium solani dropped from 36.25% to 15%, while survival rates soared to 70% compared to 42.5% in untreated plants.

Similarly, plants exposed to Sclerotium bataticola saw survival rates jump from 37.5% to 65% with BBF treatment. Beyond disease control, the BBF significantly enhanced plant growth.

Treated plants developed longer roots (37% increase), more branches (35.6% increase), and heavier pods (103.7% increase) compared to untreated ones.

These improvements were linked to the bacterium’s production of IAA, which stimulated root development, and enzymes that fortified the plants’ natural defenses (innate ability to resist pathogens).

Field Trials Transforming Real-World Farming

Encouraged by these results, the team moved to field trials (large-scale tests in actual farming conditions) conducted in Ismailia, Egypt, where peanuts are grown in sandy loam soil (a mix of sand, silt, and clay) under natural conditions.

Over four months, researchers monitored the effects of BBF on crop health, yield, and nutritional quality. The outcomes were transformative.

In fields treated with 2% BBF, seed rot incidence (percentage of infected seeds) plummeted from 28.2% to 1.6%, and root rot decreased from 16.1% to 3%.

Meanwhile, peanut plants treated with BBF grew taller (39.27 cm vs. 29.73 cm in controls), developed more branches (9.4 vs. 6.93 per plant), and produced nearly double the number of pods (82.67 vs. 50.47 per plant).

• Most impressively, pod yields (total weight of pods per hectare) skyrocketed by 113.8%, reaching 7,750 kilograms per hectare compared to 3,625 kilograms in untreated fields.

The BBF also improved the nutritional profile of the peanuts, increasing oil content from 38.1% to 44.3% and protein content from 25.2% to 29.8%—a critical advancement for addressing malnutrition in regions reliant on peanuts as a dietary staple.

Mechanisms of Action How BBF Outperforms Chemicals

The success of the BBF lies in the multifaceted way Serratia proteamaculans Sp77 interacts with plants and pathogens. First, the bacterium produces chitinase and protease, enzymes that degrade the cell walls of fungi, effectively crippling their ability to infect plants.

• Chitinase specifically targets chitin, a tough carbohydrate that forms the structural backbone of fungal cells.
• And protease breaks down proteins essential for fungal growth.

Second, it secretes 2,4-Di-tert-butylphenol, a compound identified through GC-MS analysis (Gas Chromatography-Mass Spectrometry, a technique to identify chemical substances) as a potent antifungal agent.

This compound accounted for 12.08% of the metabolites in Sp77 and has been shown to disrupt fungal membranes. Third, the bacterium’s production of IAA promotes robust root systems, enabling plants to absorb more water and nutrients from the soil.

Additionally, BBF-treated plants exhibited higher activity of defense-related enzymes like polyphenol oxidase (PPO) and peroxidase (POD), which prime the plant’s immune system (biological processes to fight infections) to respond more effectively to infections.

Advantages Over Traditional Fungicides

When compared to traditional chemical fungicides, the BBF offers clear advantages. Not only is it cheaper to produce, but it also avoids the environmental harm associated with synthetic chemicals.

For instance, Rhizolex-T 50% WP can contaminate water sources and harm beneficial soil organisms (e.g., earthworms and nitrogen-fixing bacteria), whereas the BBF supports soil health by introducing beneficial bacteria.

Farmers also benefit from the ease of application—granules can be mixed with seeds during planting or applied directly to the soil, fitting seamlessly into existing agricultural practices.

Perhaps most importantly, the BBF does not contribute to pathogen resistance, a growing problem where fungi evolve to survive chemical treatments. By leveraging natural microbial interactions, this bioformulation provides a sustainable, long-term solution to crop protection.

Challenges and Future Directions

Despite its promise, scaling up the BBF for global use presents challenges. Long-term studies are needed to confirm that the benefits persist over multiple growing seasons, particularly in diverse climates and soil types.

Researchers also aim to optimize the granule formulation to extend its shelf life (duration the product remains effective) and ensure consistent bacterial viability under varying storage conditions.

Future work will explore whether Sp77 can be used to protect other crops, such as soybeans or chickpeas, which face similar threats from soilborne fungi.

Additionally, genetic engineering could further enhance the bacterium’s ability to produce growth-promoting hormones and antifungal compounds, maximizing its effectiveness.

Global Implications for Food Security and Sustainability

The implications of this research extend far beyond peanut farming. With global peanut production exceeding 45 million tons annually, widespread adoption of the BBF could reduce post-harvest losses (crop waste after harvesting) by an estimated $1.2 billion per year.

The increased oil and protein content of treated peanuts could help combat malnutrition (lack of proper nutrients) in developing regions, where peanuts are a dietary staple.

Environmentally, replacing synthetic fungicides with bioformulations like BBF could reduce agriculture’s carbon footprint (total greenhouse gas emissions) by 15–20%, contributing to global efforts to combat climate change.

For smallholder farmers, the higher yields and reduced costs associated with BBF could lift incomes and improve livelihoods, fostering economic stability in rural communities.

Conclusion

In conclusion, the development of the Serratia proteamaculans BBF represents a major leap forward in sustainable agriculture (farming that meets current needs without harming future generations). By harnessing the power of a naturally occurring bacterium, researchers have created a tool that addresses three critical challenges at once disease control, yield improvement, and nutritional enhancement.

This innovation aligns with global initiatives like the United Nations’ Sustainable Development Goals (SDGs), which emphasize the need for eco-friendly farming practices and food security. As lead researcher Dr. WesamEldin Saber noted, “Nature’s solutions are often the most powerful. With BBF, we’re not just growing peanuts; we’re growing hope.”

For farmers, scientists, and policymakers alike, this breakthrough offers a roadmap for building resilient food systems that protect both people and the planet.

• Source: https://cultivationag.com/seed-derived-bacterial-bioformulation-improves-peanut-growth-and-fungal-defense/