Evaluating UV-C Sensitivity of Calonectria pseudonaviculata in Model Buffer Solution Using UV-C Light-Emitting-Diode System.

ABSTRACT

Calonectria pseudonaviculata, responsible for boxwood blight, produces sticky conidia that pose a contamination risk in boxwood production, cross-contamination tools and equipment and other resources. This study evaluated UV-C LED irradiation (263-287 nm) as a disinfection method by examining its effectiveness in inactivating conidia and determining the UV-C sensitivity. Conidial suspensions were exposed to quantifiable UV-C doses under dynamic stirring condition. Average volumetric intensity was quantified by accounting for UV gradients and UV dose was calculated as a product of average fluence rate (mW/cm2) and exposure time (s). UV-C irradiation effectively inactivated the tested pathogen following log-linear + shoulder kinetics as identified by parameters of goodness of model fit (i.e. high R2 and low RMSE values). The model predicted the UV sensitivity of C. pseudonaviculata conidia as 46.6 mJ/cm2/log. A total of 2.04 log reductions of the population could be obtained by an exposure of 60 mJ.cm-2 of UV-C dose. The calculated D10 was 13.53 ± 0.98 mJ.cm-2 (R2 = 0.97, RMSE = 0.14), Kmax = 0.17 ± 0.01, and shoulder length (Sl) = 33.06 ± 1.81 mJ.cm-2. These findings indicate that UV-C irradiation could be a viable option for disinfecting tools, equipment, and possibly propagation cuttings in nurseries.