Crop losses and quality degradation caused by fungal plant diseases are major constraints to food security globally. Botrytis cinerea and Alternaria alternata are the two most important fungal pathogens that can cause severe pre and post-harvest losses in strawberry and grape industry. A series of experiments were conducted to examine the potential of optical radiation and its interaction with storage temperature on suppression of gray mold development.
In vitro (Petri dish) experiments in controlled climate chambers showed that brief daily exposure of 2, 4 or 8 min of UV at an irradiance of 8 ± 1 µmol/m2/s can suppress conidial germination and colony density at room temperature (21±1 °C) in a dose dependent manner, compared with no UV control. Additional in vitro experiments were conducted with brief daily UV exposure of 8 min in combination with room temperature (21±1 °C) or cold storage temperature (4±1 °C) for 12 days. Results showed that no colony growth when the samples were exposed to UV in combination with cold storage temperature. Suppressed colony growth (colony area) with no conidiation was recorded under cold storage temperature without UV. Brief UV in combination with room temperature showed suppression in colony growth and density. Well-developed colonies were recorded under room temperature with no UV.
Similar experiments with visible blue, green, or red light at an irradiance of 100 ±10 µmol/m2/s showed no suppressive effect of blue, green, or red light on colony area and density at room temperature. On the other hand, blue light in combination with cold storage temperature showed significant suppression of colony growth and density with no conidiation.
Wavelengths of UV and blue were tested in combination with room or cold storage temperature for severity of gray mold and postharvest quality of the commercial strawberry cultivars Favori and Murano. All inoculated berries stored at room temperature with dark or blue light were full of gray mold with complete loss of integrity. UV or blue light in combination with cold storage showed very low level of severity with commercial value close to freshly harvested non inoculated berries.
Strawberry and grape are the two most important fruit crops grown worldwide for fresh and processed market. Botrytis cinerea and Alternaria alternata are the two most important fungal pathogens that can cause severe pre and post-harvest losses in this industry. At present, intensive use of fungicides and preservatives are inevitable in minimizing these losses. This endanger the UN sustainable development goal of ensuring food security by providing safe food. In this project, we will study the possible replacement of fungicides and preservatives by environmentally friendly optical radiation based strategies. While expanding the potential of optical radiation based strategies to another most important fungal pathogen Alternaria alternata, we will strengthen its practical application efficiency by exploring the i) possible role of melanin in UV screening and optical tolerance of Botrytis species, 2) storage temperature and its interaction with optical radiation in disease management efficiency, 3) selection and optimization of photosensitizer that can be exited with previously optimized optical wavelength range against powdery mildew management (250 nm-280 nm, 550 nm-660 nm), 4) effect of optical treatment on accumulation of secondary metabolites (anthocyanin, flavonols and toxins) and its potential impact on human health.