Abstract
Short-wave ultraviolet (UV-C) treatment represents a potent, clean and safe substitute to chemical sanitizers for fresh fruit preservation. However, the dosage requirement for microbial disinfection may have negative effects on fruit quality. In this study, UV-C was found to be more efficient in killing spores of Botrytis cinerea in dark and red light conditions when compared to white and blue light. Loss of the blue light receptor gene Bcwcl1, a homolog of wc-1 in Neurospora crassa, led to hypersensitivity to UV-C in all light conditions tested. The expression of Bcuve1 and Bcphr1, which encode UV-damage endonuclease and photolyase, respectively, were strongly induced by white and blue light in a Bcwcl1-dependent manner. Gene mutation analyses of Bcuve1 and Bcphr1 indicated that they synergistically contribute to survival after UV-C treatment. In vivo assays showed that UV-C (1.0 kJ/m2) abolished decay in drop-inoculated fruit only if the UV-C treatment was followed by a dark period or red light, while in contrast, typical decay appeared on UV-C irradiated fruits exposed to white or blue light. In summary, blue light enhances UV-C resistance in B. cinerea by inducing expression of the UV damage repair-related enzymes, while the efficiency of UV-C application for fruit surface disinfection can be enhanced in dark or red light conditions; these principles seem to be well conserved among postharvest fungal pathogens.
Highlights
Fresh fruits and vegetables are rich in moisture and nutrients, and susceptible to postharvest decays caused by microbial contamination and proliferation, especially pathogenic fungi (Sperber et al, 2009)
In the UV-C sensitivity assay, wild type spores of B. cinerea were completely killed by 0.8 kJ/m2 UV-C in dark and 2 h red lighttreated groups, while the spores exposed to white and blue light survived by more than 40%
Since blue light is known to be sensed by fungi via the White collar complex (WCC) photoreceptors, the WC-1 homolog gene in B. cinerea, Bcwcl1 (Canessa et al, 2013), was disrupted by replacing the open reading frame with the hygromycin resistance cassette via homologous recombination. bcwcl1 mutant strains were confirmed by genomic PCR, and showed enhanced melanization
Summary
Fresh fruits and vegetables are rich in moisture and nutrients, and susceptible to postharvest decays caused by microbial contamination and proliferation, especially pathogenic fungi (Sperber et al, 2009). Chemical sanitizers are commonly used for disinfection of the harvested crops. The long-term use of chemical fungicides frequently poses the risk of fungicide resistance in pathogens. Pesticide residue in fresh crops is an increasing health concern among consumers. To address these issues, developing alternative methods to synthetic fungicides for disease management purpose is in urgent need (Romanazzi et al, 2012, 2016). Ultraviolet-C (UV-C, 200–280 nm) offers interesting possibilities for postharvest disease management as a safe alternative to conventional chemical fungicides.
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