Plant Beneficial Microorganisms Seed Coating, a Sustainable Technology for Current and Future Agricultural Challenges

To cope with the growing demand for sustainable agricultural practices, various technologies and products have bridged the gap between research and market in recent years. One of the most promising is the use of Plant Beneficial Microbes (PBMs), such as plant growth-promoting bacteria, rhizobia, Arbuscular Mycorrhizal Fungi (AMF) and Trichoderma, to reduce the use of agrochemicals and increase plant yields, nutrition and tolerance to abiotic stresses. PBMs are considered natural alternatives to help ease pressure on the environment resulting from conventional farming. These microbes can help plants maintain or increase productivity while reducing the use of agrochemicals, restoring soil fertility, and/or overcoming problems caused by abiotic and biotic stresses.

Regulatory changes, economic instabilities and technological advancements, as well as increasing awareness among farmers, have opened the door for PBMs to become alternatives to help reduce and, in some cases, avoid the use of ecologically damaging agrochemicals. Today, the market for sustainable agricultural products includes various plant protection products, plant biostimulants and plant growth promoters. In the category of plant biostimulants and plant growth promotion, first generation products include blends and mixes of plant and root growth promoting substances, such as humic acids, algae extracts, plant extracts and biochars. More advanced versions, whether second and third generation products, include formulations combining efficient PBMs formulations that act as soil microbiome promoters and re-generators. These products are often found in liquid and water-soluble formulations and granular, pelletized and seed coating products. For the latter, the seed coating is in fact one of the most promising and efficient application technologies.

Seed coating is an efficient delivery system for PBMs

Seed coating, a process that consists of covering seeds with low levels of exogenous materials, is gaining attention as an efficient delivery system for PBMs. Seed coating facilitates direct soil inoculation, to introduce large amounts of microbial inoculants into the soil while avoiding damage to fragile seeds and protecting the inoculant from inhibiting compounds applied or produced by the seed. Seed coating can vary from simple on-farm applications to sophisticated and industrialized procedures. Although the processes used by farmers and industrial companies may differ, the basic principle is the same.

In addition to environmental advantages, seed coating also offers economic benefits, such as allowing farmers to reduce application rates and repetitions, saving machinery, fuel and labour-related costs, which are in fact the main concerns of farmers around the world. Seed coating provides the opportunity to apply effective and targeted micro-doses, reduce the level of leaching out and preventing the inefficient application of products. The right combination of PBM with biostimulant formulations applied via seed coating can be a powerful tool to help crops in terms of improving seedling establishment and germination and achieving high yields and food quality, while reducing chemical fertilization. Moreover, in more advanced technologies, such as smart farming practices, the use of seed coating is favored, due to the targeted and efficient application possibilities it offers.

Although arbuscular mycorrhizal fungi are small, they are mighty!

Among PBMs, fungi play key roles in plants and, subsequently, in humans. For over 400 million years, arbuscular mycorrhizal fungi have been forming symbiotic relationships with plants around the globe. Found on almost every continent and in approximately 90 % of vascular plants, these important fungi play a key role in plant nutrient uptake in diverse ecosystems. They begin their life in the soil in areas where roots grow. AMF are biological symbiotic soil fungi that colonize plant root systems and act as living extensions of roots, drastically increasing the absorptive surface area and improving the plant’s nutrient and water efficiency. Data have shown that mycorrhizal fungi offer a range of direct and indirect benefits to host plants through this symbiosis, and ultimately increase overall vitality, stress resilience, drought resistance and transplant success. They can also reduce investments in other important production inputs, such as fertilizers and irrigation.

Plants release hormones that help the fungi grow and increase the chances of root-fungi interaction. Additional molecules also play an important role, and German biotech pioneer Inoq GmbH holds a patent for interesting sugar molecule in this area. Once the fungi and plant roots come together, the fungi penetrate root cells then create and establish incredible structures called arbuscules, which are named for their tree-like structure.

Intraradical mycelium with arbuscules

Extraradical spores (AMF; Rhizoglomus irregulare)

Due to their many branches, arbuscules have a high surface area, allowing them to efficiently exchange many types of nutrients with plants. Arbuscular mycorrhizal fungi are known for increasing uptake of phosphorous in the plants they interact with. They can also facilitate the greater uptake of nitrogen, potassium, zinc and other nutrients. In exchange, the host plant provides food to the arbuscular mycorrhizal fungi by sharing products it makes during photosynthesis, such as lipids and sugars.

Meanwhile, in the soil, arbuscular mycorrhizal fungi form an extensive network of hyphae. ″The branched hyphal system acts as an extension of the root system, offering greater access to nutrients that would have otherwise been out of reach. This longer extensive hyphal system can reach into soil pores that were previously too small for the root system to explore. Although arbuscular mycorrhizal fungi are small, they are mighty!″ said Dr. Carolin Schneider, founder and CEO of Inoq GmbH. One gram of soil can contain between one to 20 meters of hyphae. The microscopic fungi can also dramatically improve nutrient uptake by host plants.

″The branched hyphal system acts as an extension of the root system, offering greater access to nutrients that would have otherwise been out of reach. This longer extensive hyphal system can reach into soil pores that were previously too small for the root system to explore. Although arbuscular mycorrhizal fungi are small, they are mighty!″

——Dr. Carolin Schneider
Founder and CEO of Inoq GmbH

Sometimes referred to as ″living fertilizers,″ arbuscular mycorrhizal fungi can maintain yield while reducing the need for fertilizers and boosting nutrient and water uptake, as well as improving soil structure. They even have been shown to improve plant responses stresses, such as soil salinization, heavy metal contamination and extreme temperatures.

With their known benefits, it is no surprise that researchers are looking to further understand how to protect and take advantage of these powerful and ancient fungi, to improve crop productivity in degraded soils and a changing climate.

The use of AM fungi and other microbes in seed coating are of considerable relevance to agricultural systems, especially witn the reduced use of agrochemicals, due to their role in increasing nutrient uptake and acquisition. As well as their structural and nutritional benefits, AM fungi can help crops cope with environmental stresses, therefore, improving plant growth by producing metabolites, such as amino acids, vitamins, phytohormones and antioxidant enzymes, as well as adjusting plant physiological status, such as proline content, carbon dioxide exchange rate and stomatal conductance. For example, different AM fungal species, like the ones contained in Inoq products, including Glomus intraradices, Rhizophagus irregularis, Funneliformis mosseae (formerly Glomus mosseae) and Rhizophagus fasciculatus, have been used to improve crop performance under salinity and drought stresses.

Inoq Advantage - a new mycorrhizal inoculant product for professional use

Inoq GmbH, located in the north of Germany, was founded in 2001 grounded on research and development and has been revolutionizing the industry ever since. In its latest advancement in advancing mycorrhizal inoculant technology, Inoq released Inoq Advantage, which is a new mycorrhizal inoculant product for professional use with a grain size up to < 200 µm, ideal for using in seed coating. The new addition to the Inoq product line can also be suspended for fertigation and contains an unrivaled concentration of active ingredients.

New mycorrhizal inoculant product - Inoq Advantage

″Inoq Advantage offers many advantages to growers, including its ability to be added to a liquid fertilizer stock tank and applied with a liquid fertilizer feed, which provides application efficiency and labor savings,″ said Dr. Miguel Arato, Business Innovation Manager of Inoq GmbH. ″This next-generation formulation has been successfully implemented in the agriculture markets for several years.″

″Inoq Advantage offers many advantages to growers, including its ability to be added to a liquid fertilizer stock tank and applied with a liquid fertilizer feed, which provides application efficiency and labor savings.″

——Dr. Miguel Arato
Business Innovation Manager of Inoq GmbH

Inoq Advantage is designed to enable medium to large-scale growing operations to incorporate mycorrhiza into their growing protocols efficiently and effectively, while avoiding any additional labor-intensive steps in their production protocols. With a high concentration of active ingredients, Inoq Advantage is the outcome of years of R&D, to become the most user-friendly mycorrhizal inoculant available, and it is ″Made in Germany.″ It can also be seamlessly added to crop production practices without the need for any additional steps in the production protocol. Inoculation can be achieved with irrigation or fertilizer application via boom spray, sprinkler, drip irrigation, hand spray, in-furrow or any method that effectively drenches the root zone of crop plants, ensuring direct contact between the propagules and the growing roots. The formulation is also ideal for in-field application for turf or landscape.

For 20 years, Inoq GmbH has been a pioneer dedicated to the commercial application of AMF, with in-house scientists and additional collaborations with the most well-known universities in the world. It offers its cost-effective mycorrhizal inoculants to mainstream agriculture to help increase yields while reducing the use of fertilizers, mitigating the effects of drought, and permanently sequestering carbon. The flagship product family, Inoq Advantage, is based on naturally robust strains of mycorrhizal fungi that are symbiotic with 90% of plant species, offering the most efficient and effective solution to a diverse range of crops and growing areas.The symbiotic soil organisms in Inoq Advantage are included at a very high concentration of 90.000 mycorrhizal units (MU) per g, while its best competitors have only 20.000 MU/g, many even less.

From the lab to the field, challenges still exist

As phosphorus prices increased last year, farmers around the world have added biologicals to replace a significant portion of their chemical fertilizer use. While many biologicals offer a strong substitute to chemical fertilizers, including phosphorus, only mycorrhizal inoculants give farmers an additional opportunity to increase climate resilience and access new revenue streams as a long-term strategic investment.

Despite promising results, there are still challenges, mainly related to scaling up from the laboratory to the field and proper formulation, including efficient microbial combinations and coating materials that can result in extended shelf-life of both seeds and coated PBM. Today, a growing number of PBM based products are available in the market, and most formulations based on plant growth-promoting bacteria and rhizobia. Fewer formulations in the market include AM fungi in their catalogues, due to the challenges posed by the production of high-quality AM inoculum. In most cases, leading global agricultural biostimulant companies are developing strategic alliances with trusted producers of high-quality concentrated AM fungi inoculum for their formulations, which include technical assistance and the co-development of optimal formulations of microbiome promotion products. For companies in Asia and India committed to quality products, these alliances with recognized AM firms have created opportunities to further expand their coverage and promote the use of sustainable agriculture in the growing market of PBM based biostimulants.

INOQ GmbH, the global pioneer in the research and development of high-quality AM inoculum, has recently developed new products that offer the possibility of efficient formulations for PBM seed coating products with effective AM inoculum. For more information, visit https://inoq.de.

INOQ team

This article was initially published in AgroPages' '2022 Seed Treatment Special' magazine.