Nature's approach to crop management Germain’s Technology Group Successes and challenges Applying microorganisms directly to seed can deliver a specific beneficial effect in a targeted fashion with limited environmental impact. This process however presents a special set of technical constraints. When seed is inoculated at some distance from the time and location of sowing the inocula must be able to survive on seed at low moisture levels and ambient temperatures. Fungi and some bacteria produce resistant spores that can survive these seed storage conditions.

Colonies of Rhizobium reisolated from stored soybean

They can also withstand the conventional seed treatment processes of pelleting and filmcoating, making them ideal candidates for commercial application to seed. Spore preparations of both fungi (Trichoderma and Pythium species) and bacteria (Bacillus species) have been successfully applied to a variety of crop seed using these commercial techniques.

Certain non-spore forming beneficial bacteria, such as Rhizobial inoculants, have also been successfully applied to seeds in this way. In cases where the compatible Rhizobial strains of the crop are relatively robust, seed can be preinoculated (encrusted) many weeks before planting. New filmcoating polymer techniques are being introduced to achieve seed preinoculation benefits for crops such as soybean.

However, other non-spore forming bacteria, such as the pseudomonads, have difficulty maintaining viability on stored seed and have proved highly susceptible to these commercial application processes. Unfortunately, many of the most promising root-colonizing and plant growth-promoting biocontrol agents belong to this group of bacteria. This presents a significant challenge in the use of seed treatments as a delivery system for such beneficial bacteria.

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