Wavelength dependent recovery of UV-mediated damage: Tying up the loose ends of optical based powdery mildew management

Functional Characterization of Pseudoidium neolycopersici Photolyase Reveals Mechanisms Behind the Efficacy of Nighttime UV on Powdery Mildew Suppression

“…This study indicates that the photolyase of P. neolycopersici has a broad action spectrum ranging from around 365 to 454 nm. This action spectrum perfectly overlaps with the previously published germination recovery action spectra of P. neolycopersici ( Figure 6B) (Suthaparan et al, 2018). The UV-A/blue range (peak wavelengths of 365 and 400 nm) resulted in larger colonies as compared to pure blue light (peak 454 nm) ( Supplementary Figure S9).…”

“…Brief exposure to UV during dark or in combination with red light showed higher disease control efficacy than exposure to UV in the presence of light with wavelengths shorter than 500 nm. Furthermore, using growth lights with an increased proportion of wavelengths below 500 nm immediately following the UV treatment decreased the efficacy of the nighttime UV treatment against powdery mildew (Suthaparan et al, 2017(Suthaparan et al, , 2018. This confirmed that recovery of germination in P. neolycopersici conidia treated with brief UV is dependent on the wavelength, and indicates the presence of possible light-mediated repair mechanisms of UV-induced damage in the powdery mildews (Suthaparan et al, 2018).…”

“…Our study showed that transcriptional upregulation of P. neolycopersici photolyase starts immediately after the brief UV-C exposure, both under subsequent incubation in darkness and in UV-A/blue light, and the upregulated expression is maintained for at least 8 h. Expression was also upregulated under subsequent incubation in red light, but after 8 h it was back to the level of the non-UV treated control. Previously, we have shown that incubation of UV-damaged P. neolycopersici conidia in UV-A/blue light can mediate gemination recovery of conidia, while incubation in darkness or red light cannot (Suthaparan et al, 2018). Taken together, our results suggest that (1) photolyase gene expression is induced by the brief UV-C exposure itself and that photolyase gene expression alone is not sufficient for gemination recovery of conidia, (2) UV-A/blue light provides the necessary energy for functional activity of photolyase that mediates germination recovery, (3) the inability of red light to provide necessary energy for functional activity of photolyase may prevent germination recovery, (4) red light dependent downregulation of the photolyase expression, which was induced by UV-C may further enhance this effect.…”

“…Immediately after treatments, plates were sealed and transferred to complete darkness or one of four different incubation wavelengths (365, 400, 454, and 525 nm) with an irradiance of 50 ± 5 µmol m −2 s −1 for 16 h followed by 8 h of darkness at temperature and relative humidity (RH) of 20 ± 1 • C and 75 ± 5%, respectively. Germination of conidia was assessed 24 h after inoculation (Suthaparan et al, 2018).…”

“…Extensive research has examined the potential of different spectral qualities, irradiance levels and duration of irradiance in control of powdery mildews for a wide range of crops (Suthaparan et al, 2010(Suthaparan et al, , 2012a(Suthaparan et al, , 2016aVan Delm et al, 2014;Janisiewicz et al, 2016). Short wavelength (<290 nm) ultraviolet radiation (UV) and red light have shown great potential against powdery mildews (Suthaparan et al, 2012a(Suthaparan et al, , 2014(Suthaparan et al, , 2016b(Suthaparan et al, , 2018. However, the efficacy of UV against powdery mildew varies depending on the spectral quality of the subsequent growth light.…”