Submitted to: Journal of Seed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2006
Publication Date: 10/10/2006
Citation: Kovach, D.A., Mcclurg, S.G., Widrlechner, M.P., Brenner, D.M., Gardner, C.A. 2006. Liquid nitrogen controls seed-borne chalcids without reducing germination in coriander seeds. Journal of Seed Science and Technology. 34:669-679. Interpretive Summary: Coriander seeds are susceptible to infestation by very small wasps (chalcids) which feed on seeds and destroy them. Controlling this wasp in coriander seeds is necessary to prevent spread of the insect and ensure the distribution of high-quality seed to requestors throughout the world. The discovery of wasp infestations in coriander seed samples produced at the USDA-ARS North Central Regional Plant Introduction Station, in Ames, Iowa, led us to begin experiments with the goal of developing methods for the effective control of the wasps without harming the seeds. Storing the seeds in very cold temperatures above liquid nitrogen for 16 hours proved effective in killing the wasps at all life stages without reducing seed germination, even for seed samples of low initial quality. Tests results were based on three methods: wasp emergence from the seed, hand dissections and visual inspections, and X-ray imaging. All three methods verified that these low temperatures killed the wasps, regardless of whether the insect was in the larval or adult stages. This method is simple and safe and can easily be applied by managers of seed collections, both at gene banks and within the seed industry.
Technical Abstract: Coriander (Coriandrum sativum) seeds are susceptible to infestation by chalcid (Systole) wasps which often render the seeds inviable. Control of chalcids in seeds is a prerequisite for supplying coriander germplasm to requestors throughout the world. Levels of chalcid infestation in coriander seed samples produced at the USDA-ARS North Central Regional Plant Introduction Station, in Ames, Iowa, led us to initiate experiments with the goal of developing an effective control strategy without harming the seeds. Storing the seeds above liquid nitrogen for 16 hours proved effective in killing chalcids at all life stages without reducing seed germination, even for seed samples of low initial quality. Hand dissections and visual inspections both verified the effectiveness of LN2 in killing chalcids in coriander seeds. The LN2 was effective in killing chalcids, regardless of life-stage. The use of X-ray imaging was shown to be useful for estimating insect infestations. However, the double-seed arrangement of coriander fruits made precise interpretation of X-ray images difficult.