Author
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Janisiewicz, Wojciech |
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Takeda, Fumiomi |
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Submitted to: IOBC/WPRS Bulletin (Abstract for Conference Proceedings)
Publication Type: Proceedings Publication Acceptance Date: 3/23/2018 Publication Date: 5/29/2018 Citation: Janisiewicz, W.J., Takeda, F. 2018. PhylloLux, an alternative technology to synthetic fungicides for controlling major diseases of strawberries. IOBC/WPRS Bulletin (Abstract for Conference Proceedings). 133:170-171. Interpretive Summary: Technical Abstract: Gray mold (caused by Botrytis cinerea), anthracnose (caused by Colletotrichum acutatum) and powdery mildew (caused by Podosphaera aphanis) are major diseases of strawberry causing a reduction in fruit quality and yield and/or fruit decay during production and after harvest, resulting in significant economic losses (Burlakoti, et al., 2013; Maas 1998). As much as 80% of fruit decay from gray mold after harvest result from flower infection, thus the control measures must start early in the growing cycle. Conventional control of strawberry diseases with fungicides faces several problems, mainly the development of resistance to fungicides by the pathogens, mandatory time requirements before reentry after application, an increasing public demand for produce free of pesticides, and restrictions on the use of fungicides especially in protected culture (Pokorny et al., 2016). Alternative approaches such as using biological control agents have made significant progress; however, they alone have not been as effective as fungicides and have been rarely implemented (Moser et al., 2008). Control of strawberry fruit decays after harvest with ultraviolet C (UVC) irradiation has had limited success but in combination with heat treatment and pulsed white light control was significantly improved (Marquenie et al., 2003). In general, the UVC treatment has been used only sporadically to kill plant pathogens in order to control plant diseases mainly because of its phytotoxicity at doses required to kill pathogens and the high cost of electricity. We developed PhylloLux© technology, a new approach using UVC irradiation to kill pathogenic fungi by including a dark period and application of antagonists after irradiation (Janisiewicz et al., 2016 a, b). The dark period for a specific time (2-4 hours depending on the pathogen) immediately after irradiation with UVC prevented the fungi from activating light induced enzymes involved in repairing their DNA damaged by the UVC irradiation. This allows to kill fungi with much lower UVC doses. The irradiation doses did not affect pollen germination rate, tube growth and fertilization of flowers, nor had any negative effect on the photosynthetic apparatus in leaves or quality of strawberry fruit. Gray mold, anthracnose and powdery mildew all were greatly reduced in greenhouse and high tunnel studies with night time UVC irradiation for 60 seconds (12.3 J/m2) twice a week. A single postharvest UVC/dark treatment of wounded strawberries artificially inoculated with B. cinerea resulted in almost complete control of gray mold. Fruit harvested from UVC/dark treated strawberry plants looked heathy in contrast to plants not treated with UVC which were smaller, often cracked and without luster, which are typical signs of powdery mildew. Positioning of the UVC bulbs over the top of strawberry plants had a significant effect on reducing powdery mildew which was visibly more apparent on adaxial than on abaxial side of the leaves. Reflecting surfaces are being tested to improve UVC penetration into the plant canopy. The UVC irradiation creates a microbial void that has the potential to cause shifts in strawberry microbiota that may unintentionally favor human and/or plant pathogens. To prevent this and further increase the robustness of the disease control, we applied two antagonists, Aureobasidium pullulans and Metschinikowia pulcherrima, after UVC treatment. These antagonists were originally isolated from fruits and effectively controlled postharvest decays of various fruits in our earlier research. In the present study, both antagonists efficiently colonized strawberry plants, with M. pulcherrima being a superior colonizer of anthers and entire flowers and A. pullulans effectively colonizing leaves. In strawberry petal tests, both antagonists significantly reduced gray mold originating from ino |
