Assessment of novel ι-carrageenan hydrogel blends as environmentally friendly seed coating agents for durum wheat seeds Maya Hotta B.Sc. (Hons) Athlone Institute of technology Supervisors: Dr. Noreen Morris Dr. James Kennedy Prof. Clement Higginbotham Supervisors: Dr. Noreen Morris Dr. James Kennedy Prof. Clement Higginbotham

Feeding 9 Billion People… United Nations1 estimated human population to reach 9.6 billion by the year 2050 Food production must increase to meet food demand Pollution caused from agriculture is currently a major concern Climate change – drought also becoming a threat Greener solutions without reducing food productivity is essential Hydrogels are potential materials for sustainable agriculture

What is a Hydrogel? Polymers forming a gel-like material Absorbs fluid into its 3D network Takes up water from 20 % up to thousands of times their dry weight2 Releases water when exposed to dry environment Fig. 1 Dry hydrogel (left) swells (right) after soaking up water3.

Agriculture/Horticulture application Hydrogels are used as soil conditioners or “water crystals” Works as water reservoir for plant growth Plants can grow in dry sandy soils Helps water conservation Target delivery systems Controlled pesticide/nutrient release Reduces application frequency Minimize spreading of toxic materials and exposure Helps environment and soil conservation Fig. 2 Hydrogels known as water crystals4.

Iota-carrageenan Fig. 3 Carrageenan5 (right) obtained by extraction with water or aqueous alkali from some members of the class Rhodophyceae6 (left). Natural polysaccharide derived from red seaweed (Fig. 3) Cheap Eco Friendly Non-toxic Easy to handle 1% (w/v) ι-carrageenan hydrogel had shown promising results: Faster and higher seed germination rate (Fig. 4) Fig. 4 Grass growing better in the presence of 1% (w/v) ι-carrageenan hydrogel (right) but less in the pot without the hydrogel (left).

Hypothesis Ι-Carrageenan hydrogel coating on seeds can contribute in sustainable agriculture by: Speeding up germination Promoting seed growth in dry soils Reducing amount of water required for crops Biodegradable and non-toxic Minimize environmental impact Low material cost* * 1KG of ι-Carrageenan cost €231.67 from Sigma Aldrich (Purchased 2013)

Problems with ι-carrageenan Fig. 5 Re-swelling studies of ι-carrageenan (left) and agar (right) compared after 1 hr in distilled water. Very weak hydrogel Dissolves too fast in water Evaporates water quickly at 30°C

Project Aim Formulate new seed coating agent based on ι-carrageenan: Increase gel strength Prolong hydrogel life-span in excess water Increase water retention capacity (30 °C) Maintain environmental friendliness All ingredients natural, non-toxic and Composition based on synergistic effect between polysaccharides Evaluate two hydrogel blends for seed coating application Germination tests on commercially important seeds Film coating seeds with conventional coating methods

Development of new hydrogels Two hydrogel blends were prepared for analysis: Table 1. The composition of hydrogels tested for characterisation Hydrogel Code Components ι-carrageenan (%) agar (%) xanthan κ-carrageenan (%) Control 1.5 - Blend 1 1 0.5 Blend 2 0.25 Hydrogel characterisation methods: Swelling studies – Water uptake, life-span and water retention Rheological analysis – Gel strength

Characterisation Results (Refer to Table 2) 6 hr 24 hr Fig. 6 Summary of hydrogel characterisation results for control, Blend 1 and Blend 2 hydrogels *Hydrogels were observed at room temperature (< 25°C) **Hydrogels were observed at 30 °C Improvements: Blend 2 showed the highest water uptake and life-span (24hr) Blend 1 showed the highest water retention capacity Blend 2 showed the highest gel strength

Seed tests Durum wheat (Triticum durum Desf.) is a cereal crop widely cultivated today They grow in a warm, dry climate where drought may be a problem Effect of hydrogel on germination % and seed growth rate investigated The hydrogel blend type giving the best germination % was determined Conventional coating methods: spray and pan coating compared

Seed test results Effect of Hydrogels: † * ** *** Data: Mean ± SE *p < 0.05 vs Water treatment **p < 0.05 vs Blend 2 treatment ***p < 0.05 vs Water treatment †1 % (w/v) ι-carrageenan Fig. 7 Summary of seed testing results compared with four different treatment types Effect of Hydrogels: Hydrogel treated seeds performed better than distilled water Ι-carrageenan proven to increase seed germination % and speed of germination

Seed coating comparison Fig. 9 Spray coated seed with green colorant (Blend 1) Fig. 8 Non-treated seed Fig. 10 Pan coated seed with green colorant (Blend 1)

Current work… Collaboration with the Department of Agriculture and Food Laboratories (Backweston, Celbridge) Investigating optimum coating conditions Comparing natural vs. synthetic hydrogel coating effect Stress test of seeds under dry conditions

References United Nations. World Population Prospects The 2012 Revision.; 2013. Available at: http://esa.un.org/unpd/wpp/Documentation/pdf/WPP2012_HIGHLIGHTS.pdf. [Accessed October 18, 2013] Hoffman AS. Hydrogels for biomedical applications. Adv. Drug Deliv. Rev. 2012;64:18–23. Available at: http://www.sciencedirect.com/science/article/pii/S0169409X12002700. [Accessed July 14, 2014] Don Carr Company. Polymer Crystals. Water-Gel Cryst. 2014. Available at: http://watergelcrystals.com/order-crystals.htm. [Accessed September 10, 2014] HGTV Gardens. How to Plant a Container Garden - Planting a Small Container Garden. 2011. Available at: http://www.hgtvgardens.com/container-gardening/how-to-plant-a-colorful-container-garden. [Accessed September 10, 2014] PureNature. Carrageenan Gum, Iota - Gums & Resins - Raw Materials. 2013. Available at: http://www.purenature.co.nz/shop/Raw+Materials/Gums+&+Resins/Carrageenan+Gum+Iota.html. [Accessed September 10, 2014] Danisco Cultor. Introduction to GRINDSTED TM Carrageenan. 2nd ed. Danisco A/S; 2003:1–6. Available at: http://www.aditiva-concepts.ch/download/Carrageenan.pdf

Acknowledgements: President’s Seed Fund AIT and Agri Aware Department of Agriculture, Food and the Marine (Seed testing laboratory, Celbridge) Gold Crop Ltd. (Cork) RAGT Semences (France) Teagasc Oak Park Crop Research Centre (Carlow) Bejo Zaden B.V. (Netherlands)

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