BioSave 10-LP and SO2 for Postharvest Control of Muscadine Pathogens

Postharvest temperature management and chlorine washes are the primary tools available to growers for maintaining quality and controlling fungal pathogens postharvest of Muscadine grape. However, latent infections from the field by fungal pathogens Glomerella cingulata and Greeneria uvicola results in the mycelial spread and sporolation during storage.  The objective of this study was to evaluate BioSave 10LP and SO₂ for their efficacy in controlling mycelial spread and sporolation of fungal pathogens. Fruit were hand-harvested and transported to UGA where fruit were treated with 100 µL L^-1 chlorine, 4.4 g L^-1 BioSave 10LP, 250 ppm-hour SO₂ fumigation, or stored with SO₂ emitting sheets, then stored and removed bi-weekly up to 6-weeks (0-1ºC, 90 to 95% R.H.).  After removal from storage, fruit were warmed overnight (21°C), and then evaluated 1 and 4 days post-removal for firmness, soluble sugars, and titratable acids, and mold.  An artificial inoculation study was also performed where fruit were cut and inoculated with 1×10² conidia per mL of Glomerella cingulata or Greeneria uvicola, permitted to dry, then treated with BioSave 10 LP, 100 µL L^-1 chlorine, or a 240 ppm-hour SO₂ fumigation prior to being sealed in polyethylene containers under a continuous stream of humidified air.  Mycelial and spore development was monitored 1, 3 and 5 days after inoculation using a subjective score.  There was a substantial loss in firmness over the 6 weeks of storage, with the most significant drop occurring within the first 2 weeks after harvest.  Of the fruit that were treated with BioSave 10 LP, sulfur dioxide fumigation, or sulfur dioxide emanating sheets, only the latter displayed any retention in fruit firmness, reduced molds, and greater overall fruit quality.  For the artificial inoculations, it was found that all 3 treatments reduced the amount of molds when compared to the positive controls, for the first 3 and 5 days post-inoculation. Thus, sulfur dioxide, when used as a slow-release sheet placed around the packaged fruit, was very effective at controlling molds and maintaining firmness and was more effective than a one-time fumigation or a BioSave 10 LP treatment.  However, a treatment of BioSave 10 LP, chlorine or an SO₂ fumigation were effective at controlling artificially inoculated fruit for 3 and 5 days post-inoculation.  The results from this study suggest there are opportunities for the industry to help control postharvest fungal pathogens of Muscadine grape.