Microbial Seed Coating - New Horizons in Seed Coating Solutions

Co-authored by Afzal Khan and Vimala Prakash

Introduction

The demand for biological seed coating solutions is increasing. Microbes uses natural mechanisms to control pests, minimize stress and provides nutrition for better growth and yield. Seed coating with microbes is one of the foremost step in introducing the virulent and efficient microbes on the seeds. Seed coating techniques are not feasible at a commercial scale and there are significant technical challenges in maintaining viable microbes and seeds throughout commercial seed treatment processes and storage. 

The efficiency of the seed coating depend on the microbial load on seed surface and viability of coated microbes during storage and transport. To increase the efficiency of the microbial seed coating, IPL Biologicals Limited has come out with the novel method of coating the seeds with virulent and potential microbes using a unique polymer (Biocoat). 

The Biocoat developed by IPL Biologicals Limited is biodegradable in nature, provides good adhesion, provide uniform coverage, non-inhibitory to microbes, preserve microbes for long time and soluble in water (hydrophilic). The NutriBiocoat  (Biocoat + nutrition and protection providing microbes) is a novel product for the coating the seeds with virulent and potent beneficial microbes.

Benefit of Nutribiocoat:  

In addition to the normal benefits of coated seeds over uncoated seeds viz. providing protection to seeds during germination against soil-borne disease and pests leading to higher survivability, there are special benefits of using microbial seed coatings as over chemical coatings: 

• Microbes providing nutritional benefits can be coated on the seeds, which is not possible in chemical coating. These include nitrogen fixing bacteria, plant growth promoting bacteria, P & Zn solubilizing bacteria, K mobilizing bacteria among others. 

• The microbes coated on the seeds multiply profusely in the soil to populate a large root zone volume, providing nutrition and protection to the plant. In the case of chemical coating, the protection is limited to the quantity that can be coated on the small surface area of the seed. 

• The beneficial microflora in soil persists to preserve soil health

• Environmentally friendly and cost effective

The microbes’ recipe in NutriBiocoat comprises agricultural beneficially microbes like plant growth promoting rhizobacteria, bacterial biofungicide, fungal biofungicide, mycorrhiza, nitrogen fixing bacteria, phosphate (P) solubilizing bacteria, potash (K) mobilizing bacteria,  zinc (Zn) solubilizing bacteria etc. 

Stability (Shelflife) study:

47 type of combinations based on different purposes viz protection alone, protection plus nutrition have been developed and coated on different types of seeds. Microbial load and viability study was conducted and found the product (coated microbes) is stable for more than 2 years (Figure 1). 

Figure 1: Product stability in term of CFU for 2 years

NutriBiocoat efficacy trials

Numerous pot and field trials have been conducted with various crops like Corn, Wheat, Soybean, Chickpea and Paddy. Here, we present an example of Nutribiocoat’s effect on Corn seeds germination and growth in pot trial.  

A pot trail was conducted under greenhouse condition to know the effect of Nutribiocoat (having combination of VAM, Biofungicide, PGPR, ZSB and PSB) in the soil infected with Fusarium and Rhizoctonia. Non-treated seeds were taken as control. Soil was autoclaved twice to sterilize the microbial flora of the soil. Sterilized soil was infected with known concentration (CFU count 108) of pathogens. Coated and non-coated seeds were sown in triplicates in the fully infected soil (i.e. Pathogens count in per gram soil was 108). The duration of the trial was 35 days.

Higher germination i.e 90% was reported for NutriBiocoat coated seeds comparison with 76.7 % in non-coated seeds (Figure 2, Graph 1).

Figure 2: Effect of coating on seed germination

Graph 1: Effect of Nutribiocoat on different parameters during pot trial

Shoot length and root length was observed higher for Nutribiocoat during the pot trial. (Graph 1).  The shoot length 32 cm was reported in Nutribiocoat and 30 cm in control. Root length was recorded 7 cm in Nutribiocoat and 6 cm in control (Graph 1 and figure 3).

Lower incidence of dumping off (low death rate) was recorded for the seeds coated with Nutribiocoat seeds in comparison to control at post-emergence stages (Graph 1). Also the seedling vigor was recorded higher for coated seeds than non-coated seeds.  Lower damping off i.e 14 % was observed in NutriBiocoat with comparison to 26% in control.

Fig 3: Effect of coating on (a) shoot length (b) root length of corn

Conclusion

1. Microbial seed coating is a feasible mode of microbes introduction in particular for broad-scale agriculture and horticulture.

2. It is validated that microbial seed coatings of disease and pest control microbials provide effective protection to seeds against various soil-borne diseases and pest

3. It is validated that microbial coating helps in better seed germination and seedling vigour 

4. It is validated that microbial seed coatings of nutrition microbials provide significant nutrition benefit to the germinating seed and growing plant.
   

5. It is possible to combine the nutrition and protection benefit in a seed coating – a novel development that is not possible with chemical coatings.
   

All of these lead us to conclude that microbial seed coatings offer significant benefits over existing seed coatings.

IPL Biologicals Limited 5th Floor, M2K corporate park, Mayfield garden, sector 51, Gurugram, Haryana-122003, India. www.iplbiologicals.com

This article was initially published in AgroPages ‘Annual Review 2020’ magazine. Download it to read more articles.