Blue light discourages molds that spoil citrus fruit, UF researcher says

GAINESVILLE, Fla. — One species of Penicillium fungus gave humanity the miracle drug penicillin; some of its cousins give the citrus industry headaches.

Commonly known as green mold and blue mold, respectively, the fungi Penicillium digitatum and Penicillium italicum spoil recently harvested fruit. But researchers with the University of Florida’s Institute of Food and Agricultural Sciences have found an environmentally friendly way to address the problem—using blue light to activate natural defenses within the fruit.

A study published in the current issue of the journal Postharvest Biology and Technology showed that tangerines inoculated with P. digitatum spores had a 100 percent infection rate when kept in constant darkness or constant white light for six days. When kept in constant blue light the rate was 50 percent. And when kept on a schedule that alternated 12 hours of blue light exposure with 12 hours of darkness, the infection rate was only 25 percent.

These preliminary findings suggest that certain light wavelengths activate an enzyme called phospholipase, which kick-starts the tangerine’s immune response, said Jackie Burns, director of UF’s Citrus Research and Education Center in Lake Alfred and one of the study authors.

By exposing the fruit to those wavelengths on a schedule that mimics the rhythms of night and day, the scientists increased the protective effect, she said.

“I wouldn’t be surprised if these rhythms played a more prominent role in postharvest biology than we currently realize,” Burns said.

Though the system isn’t ready for use by industry, UF researchers are pursuing refinements, such as determining the shortest amount of treatment time needed to activate phospholipase.

Related UF projects are exploring the potential for blue light to discourage fungal diseases in plant nurseries, and investigating other naturally occurring compounds in citrus that may fight fungal infections.


Writer: Tom Nordlie, 352-273-3567,

Source: Jackie Burns, 863-956-5897,


Posted: October 20, 2011

Category: Agriculture, UF/IFAS
Tags: Blue Light, Burns, Citrus, Disease, Lake Alfred, Mold, Penicillium, Postharvest, Tangerine

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