Direct infusion device for molecule delivery in plants

Authors: Rhodes, Brian; STANGE, RICHARD - US Department Of Agriculture (USDA); ZAGORSKI, PATRICK - Agrosource, Inc; Hentz, Matthew; Niedz, Randall; Shatters, Robert - Bob; PITINO, MARCO - Agrosource, Inc

Submitted to: The Journal of Visualized Experiments (JoVE)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2023
Publication Date: 6/2/2023
Citation: Rhodes, B.H., Stange, R., Zagorski, P., Hentz, M.G., Niedz, R.P., Shatters, R.G., Pitino, M. 2023. Direct infusion device for molecule delivery in plants. The Journal of Visualized Experiments (JoVE). https://dx.doi.org/10.3791/64008.
DOI: https://doi.org/10.3791/64008

Interpretive Summary: Testing new chemicals on plants is an important part of plant research. Two common testing strategies are spraying the chemical on the leaves of plants and applying the chemical to the soil so it can be absorbed by the roots. These approaches can be wasteful because only a portion of the chemical goes into the plant. To create a more efficient chemical testing strategy, we have developed a direct plant infusion device that delivers chemicals directly to the trunk of the plant through a drilled hole. Most parts of this device are made in house using a nylon-based 3D printer as well as various silicone molds. This helps reduce costs and will allow future users to change the device for their specific needs. We have shown that fluorescent chemicals delivered using this device make it in to many parts of the plant. In addition, we have used our device on young citrus trees to test chemicals that have the potential to kill either the bacteria or insect that together cause citrus greening disease. Chemicals that can help control citrus greening disease are important because it is a major threat to citrus production in the United States. Although our research focuses on citrus plants and diseases, we believe this device could also be useful to other plant researchers for a variety of plant chemical testing.

Technical Abstract: Testing the function of therapeutic compounds in woody plants is an important component of agricultural research. Foliar or soil-drench methods are routine, but have drawbacks that include variable uptake and environmental breakdown of tested molecules. Trunk injection of trees is well established, but high-pressure injection can cause vascular damage and requires expensive equipment. In our laboratory, we are screening molecules for therapeutic treatment of citrus greening disease. As a screening tool, we require a simple, low-cost way to deliver putative therapeutics to the vascular tissue of small greenhouse grown citrus trees infected with a phloem-limited bacterium, “Candidatus Liberibacter asiaticus” (CLas) or the phloem feeding CLas insect vector, Diaphorina citri, Kuwayama (D.citri). To meet our screening requirements, we have designed a direct plant infusion (DPI) device that connects to a woody plant’s trunk and is made using a nylon based 3D-printing system and easily obtainable auxiliary components. The compound uptake efficacy of this device was tested in citrus plants using 5,6 carboxyfluorescein-diacetate as a fluorescent marker. Robust and uniform compound distribution throughout the plants was observed. Furthermore, we tested the viability of using this device to deliver antimicrobial and insecticidal molecules to determine their effects on CLas and D. citri respectively. We introduced a truncated derivative of the antimicrobial peptide, oncocin-112, into CLas infected citrus plants using our DPI device and observed a reduction in CLas titer after two weeks. In addition, we utilized our device to deliver a neonicotinoid insecticide, Imidacloprid, into D. citri infested citrus plants and showed a significant increase in psyllid mortality after 7 days. These results suggest that the described DPI device represents a modifiable molecule delivery system that can be used to test experimental compounds or deliver therapeutics in a commercial setting in citrus and, presumably, a wide array of other woody plant species.