Effect of LED, UV-B, and fluorescent supplemental greenhouse lights on strawberry plant growth and response to infection by the anthracnose pathogen, Colletotrichum gloeosporioides

Authors: Smith, Barbara; REZAZADEH, AMIR - St Lucie County Extension; STAFNE, ERIC - Mississippi State University; Sakhanokho, Hamidou

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2022
Publication Date: 6/28/2022
Citation: Smith, B.J., Rezazadeh, A., Stafne, E., Sakhanokho, H.F. 2022. Effect of LED, UV-B, and fluorescent supplemental greenhouse lights on strawberry plant growth and response to infection by the anthracnose pathogen, Colletotrichum gloeosporioides. HortScience. 57(8):856–863. https://doi.org/10.21273/HORTSCI16591-22.
DOI: https://doi.org/10.21273/HORTSCI16591-22

Interpretive Summary: Supplemental lighting is often used to extend daylength for strawberries grown in greenhouses and high tunnels; but only a limited amount of information is available on the effect of these lights on disease development and pathogen growth. Many types of supplemental lighting are available for use in commercial greenhouses, and LED light is frequently chosen. In this greenhouse study we investigated the effect of LED lights, wide spectrum fluorescent grow lights and UV-B light on strawberry plant growth and plant response to infection of detached strawberry leaves inoculated with the anthracnose crown rot pathogen. The study showed significant differences between the supplemental lights on strawberry plant growth, but not on anthracnose disease severity. Plants in two LED treatments displayed signs of severe injury possibly due to the high intensity of the red LED light. Installation of supplemental lighting in greenhouses requires a significant investment by the grower, and this study lays the groundwork for future more detailed studies to provide growers with the data they need to make informed decisions on which supplemental light spectra are best for each phase of strawberry production (plant growth, flowering, and fruiting) and any potential effect of the lights on diseases and insects.

Technical Abstract: Supplemental lighting is frequently used to extend day length for strawberries (Fragaria ×ananassa Duch.) grown in greenhouses and high tunnels; however, information is limited on the effect of these lights on disease development. We evaluated the effect of six supplemental light treatments [red, blue, white light emitting diodes (LEDs); a combination of red, blue, and white LEDs; wide spectrum fluorescent; and wide spectrum fluorescent + UV-B] on plant growth and plant response to infection of strawberries grown in a greenhouse. Plants received natural light supplemented by 17 hours of treatment lights. In addition, plants in the wide spectrum fluorescent + UV-B treatment were exposed to UV-B light for 3 h during the dark period. Each light treatment included four plants each of six strawberry cultivars and was replicated three times. Following 4- and 5- month exposures to light treatments, detached leaves from each cultivar in each light treatment were inoculated with the anthracnose pathogen, Colletotrichum gloeosporioides and rated for disease severity 10 days later. There was a significant difference in photosynthetic photon flux density (higher in red and combination LED light treatments), relative chlorophyll content, flower number, plant size, plant injury, and elemental leaf analysis; but there was not a significant effect of light treatments on disease severity ratings following inoculation with C. gloeosporioides. There were significant effects due to cultivar for growth and disease severity ratings, but not a significant interaction between light treatments and cultivars. This study showed an effect of supplemental light on several strawberry plant growth parameters including a harmful effect of high intensity red LED irradiation. It did not show an effect of the light treatments on plant response to infection following inoculation with an anthracnose pathogen.