The effect of plant cuitivar, growth media, harvest method and post harvest treatment on the microbiology of edible crops.

摘要

Systems for the growth of crops in closed environments are being developed and tested for potential use in space to provide a source of fresh food. Plant growth conditions, growth media composition and harvest methods can have an effect on the microbial population of the plant, and therefore should be considered along with the optimization of plant growth and yields to ensure a safe and palatable food crop. This work examined the effect of plant cuitivar, growth medium, and harvest method on plant microbial populations. Twelve varieties of leafy greens and herbs were grown in a mixture of Fafard #2 and Arcillite using the "pillow" root containment system currently being considered for the VEGGIE plant growth unit developed by Orbitec. In addition, Sierra and Outredgeous lettuce varieties were grown in three different mixtures (Fafard #2, Arcillite, and Perlite/Vermiculite). The plants were analyzed for microbial density. Two harvest methods, "multiple cuttings" and single harvestwere also compared in separate experiments. Red leaf lettuce and mizuna were grown in pots in a Biomass Production System for Education (BPSe) chamber and harvested every two weeks by either method. Another set of experiments was performed using the rooting pillows to grow five varieties of leafy greens and cut harvest at different time intervals. Radishes were harvested and replanted at two-week intervals. Results indicate up to a 3 log~(10) difference in microbial counts between some varieties of plants. Lettuce grown in arcillite rooting medium resulted in an approximately 2 log10 lower count than those grown in the other mixtures. Harvest method and frequency had less impact on microbial counts only showing a significant increase in one variety of plant. Post harvest methods to decrease the bacterial counts on edible crops were investigated in these experiments.