Seed treatment as a delivery mechanism of a beneficial fungal volatile organic compound

Abstract

The fungal volatile organic compound 6-pentyl-2H-pyran-2-one (6-PP), produced by Trichoderma spp., can enhance plant growth and resilience to abiotic and biotic stresses. Using commercially synthesised 6-PP offers a controlled, consistent and scalable alternative to live Trichoderma application. The application of 6-PP to seed is one possible delivery mechanism, but its effect on seed germination and emergence is unknown. This study assessed the effect of five rates of 6-PP (from 75 to 350 mM) on the germination of seeds of five agricultural or forestry species: Lolium perenne (perennial ryegrass), Bromus willdenowii (prairie grass), Triticum aestivum (wheat), Brassica napus (forage rape) and Pinus radiata (radiata pine). In addition, the 75 mM rate was tested on the seeds of four native New Zealand tree species: Coprosma robusta (karamū), Plagianthus regius (ribbonwood/manatu), Sophora prostrata (kōwhai) and Pittosporum tenuifolium (black matipo/kohuhu). Application at 75, 114 and 228 mM did not affect the germination of prairie grass, wheat and radiata pine. However, the germination of perennial ryegrass was significantly reduced at the 228 mM rate, and prairie grass and radiata pine at the 350 mM rate, due to the production of abnormal seedlings (stunted roots) and/or dead seeds. Germination of karamu, kōwhai and ribbonwood/manutu seeds was not affected by the 75mM rate, while black matipo/kohuhu germination was significantly increased by 164%. In five field crops of wheat and perennial ryegrass, the emergence of seeds treated with 75 mM of 6-PP was either significantly increased or did not differ from the control. Seed treatment is therefore a promising delivery method for 6-PP. Further research is needed to refine application rates, determine compatibility with agrichemicals and evaluate the storage potential of the treated seed.