By Dr. Jaimin S. Patel, Research Scientist at the Lighting Research Center, Rensselaer Polytechnic Institute
Controlled environments, including greenhouses and indoor vertical farms, have become the next-generation agricultural systems for increasing crop production capacity year-round. However, plant pathogens invariably invade these controlled environments, causing severe losses. Every year several new diseases are reported on different crops and disease-causing organisms are responsible for significantly decreased crop production. Moreover, farmers who want to grow organic crops often find that it is especially difficult to manage plant diseases in controlled environments using organic practices.
This year, I joined the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute as a research scientist. The LRC is the world’s leading center for lighting research and education, and has been pioneering research in solid-state lighting, light and health, transportation lighting and safety, and energy efficiency for nearly 30 years.
I am now collaborating with Dr. David Gadoury of Cornell University’s Division of Plant Pathology and Plant-Microbe Biology and Dr. Mark Rea of the LRC on a $1.7 million project funded by the U.S. Department of Agriculture and the National Institute of Food and Agriculture to study the novel use of light to suppress a broad group of plant pathogens in controlled environments.
Research is still underway, but preliminary results show that advanced light-emitting diode (LED) technology can provide lighting conditions that are detrimental to plant pathogens and at the same time, ideal for healthy plant growth. In this way, we can provide a tailored spectrum and duration of light at the right time of day or night to reduce plant diseases and increase yield of crops grown in controlled environments.
Until recently, most growers used fluorescent lamps, incandescent lamps or high-intensity discharge (HID) lamps in controlled environment agriculture, primarily to extend the hours of available daylight. However, in the past decade, technical developments in advanced LED lighting for horticulture applications have fueled an expansion of controlled environments for crop production. A variety of spectrally tuned LED lighting is now available to modify morphological and chemical characteristics of plants, enabling growers to extract greater value from crop production. Through my research, I have found that specific wavelengths of light can be used to defeat the downy mildew pathogen which poses substantial challenges in basil production in controlled environments.
Some pathogen groups, notably powdery mildews (Erysiphaceae), are so severe as to preclude economic production in controlled environments without intensive use of pesticides. Conventional wisdom points to the favorability of temperature and relative humidity in glasshouses as the primary drivers of powdery mildew epidemics. However, the research indicates that both visible and UV radiation have an unappreciated role as epidemic drivers. This discovery opens new possibilities to suppress plant pathogens by selective manipulation of light. While experimentally demonstrable for many years with the older lighting technologies mentioned above, such as fluorescent and HID lamps, the advancements in LED technology offer unprecedented opportunities to manipulate wavelength, pulse duration, synchrony, and novel spectral combinations to produce suppressive effects on pathogens, while maintaining plant health and productivity. Collaborative research at the LRC and at Cornell seeks to understand and exploit the foregoing light-dependent mechanisms for the purposes of suppressing plant pathogens in these challenging environments.
One of the major research programs at the LRC is the study of light on circadian rhythms. All creatures, great and small, are governed by the natural 24-hour, light-dark cycle. Every cell and physiological system in plants and animals exhibits a circadian cycle. In humans, circadian disruption is most obviously linked with disruption of the sleep-wake cycle—feeling sleepy during the day and experiencing sleep problems such as insomnia at night—but is also linked with increased risk for diabetes, obesity, cardiovascular disease and cancer.
In recent years there has been increased interest in the research community into the circadian rhythms of plants and plant pathogens. Through my research, I have observed the growth of several plant pathogens over the 24-hour day and night cycle where some pathogens produce sporulation in the dark or at night, whereas others sporulate in the light or during the daytime. To give you an example, downy mildew pathogens sporulate only during nighttime hours. Scientists have started taking advantage of this circadian cycle-associated mechanism and utilized lighting during the night to successfully prove that sporulation of downy mildew pathogens can be controlled by light.
In my previous research, I have shown that exposing basil plants to red LEDs can help to inhibit sporulation of the downy mildew pathogen (Patel et al. 2016). This is good news because growers can stop the massive production of spores that eventually become airborne and spread throughout the facility, ultimately infecting the healthy plants. The inhibition of sporulation using light can slow down the disease development process as it disturbs the lifecycle of the pathogen. This is just one benefit of light by which sporulation of pathogens can be inhibited. There are many things we do not yet know about interactions among light, plants and pathogens. Understanding how light alters plant pathogens will help to control their growth and eventually aid in the management of all plant diseases.
It is also known that ultraviolet (UV) light ranging from 200 nanometers (nm) to 380 nm in wavelength is effective in controlling many plant diseases (Janisiewicz et al. 2016; Suthaparan et al. 2012). Most powdery mildew pathogens are sensitive to UV. A short exposure of powdery mildew pathogens to UV at specific wavelengths can control powdery mildew and keep plants disease free (Suthaparan et al. 2012; Suthaparan et al. 2016). However, accurate exposure of UV is required to make sure that a plant pathogen is destroyed without damaging the plant. Once fruits and vegetables are harvested, disease free arrival of these fruits and vegetables at the market is of the utmost importance. UV treatment of fresh vegetables and fruits keeps their surface free of pathogenic organisms and therefore, increases shelf life and market values.
In the future, growers will have the opportunity to use LEDs not just for extending the period of natural daylight but also for providing lighting tailored specifically to suppress growth of plant pathogens and to extract greater value from their crops by producing healthier, more robust plants. Looking at the many advantages of advanced lighting technologies and applications for the growth and protection of plants in controlled environments, the future certainly looks bright.
Jaimin Patel, Ph.D., is a plant pathology research scientist at the Lighting Research Center at Rensselaer Polytechnic Institute. During his research career, Dr. Patel has provided disease management strategies for diseases of several crops including wheat, mustard, basil, arugula, squash, tomato and thyme, to name a few. Dr. Patel is the author of more than 40 scientific articles, and serves as the Associate Editor of Plant Health Progress, a peer-reviewed journal of applied plant health. Dr. Patel has track record of international collaborations to study multiple crops and a variety of plant pathogens.
About the Lighting Research Center
The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute is the world’s leading center for lighting research and education. Established in 1988 by the New York State Energy Research and Development Authority (NYSERDA), the LRC has been pioneering research in solid-state lighting, light and health, transportation lighting and safety, and energy efficiency for nearly 30 years. LRC lighting scientists with multidisciplinary expertise in research, technology, design, and human factors, collaborate with a global network of leading manufacturers and government agencies, developing innovative lighting solutions for projects that range from the Boeing 787 Dreamliner to U.S. Navy submarines to hospital neonatal intensive-care units. LRC researchers conduct independent, third-party testing of lighting products in the LRC’s state of the art photometric laboratories, the only university lighting laboratories accredited by the National Voluntary Laboratory Accreditation Program (NVLAP Lab Code: 200480-0). In 1990, the LRC became the first university research center to offer graduate degrees in lighting and today, offers a M.S. in lighting and a Ph.D. to educate future leaders in lighting. With 35 full-time faculty and staff, 15 graduate students, and a 30,000 sq. ft. laboratory space, the LRC is the largest university-based lighting research and education organization in the world.
Lighting Research Center
Rensselaer Polytechnic Institute
21 Union St., Troy, NY 12180
Janisiewicz, W. J., Takeda, F., Glenn, D. M., Camp, M. J. and Jurick II, M. J. 2016. Dark Period Following UV-C Treatment Enhances Killing of Botrytis cinerea Conidia and Controls Gray Mold of Strawberries. Phytopathol. 106: 386-394.
Patel, J. S., Zhang, S., McGrath, M. T. 2016. Red light increases suppression of downy mildew in basil by chemical and organic products. Phytopathol. (Accepted).
Suthaparan, A., Stensvand, A., Solhaug, K. A., Torre, S., Mortecnsen, L. M., Gadoury, D. M., Seem R. C., and Gislerod, H. R. 2012. Suppression of powdery mildew (Podosphaera pannosa) in greenhouse roses by brief exposure to supplemental UV-B radiation. Plant Dis. 96: 1653-1660.
Suthaparan, A., Solhaug, K. A., Bjugstad, N., Gislerod, H. R. Gadoury, D. M., and Stensvand, A. 2016. Suppression of powdery mildews by UV-B: Application frequency and timing, dose, reflectance, and automation. Plant Dis. 100:1643-1650.