Shortwave Ultraviolet Irradiation for Control of Decay Caused by Botrytis cinerea in Bell Pepper: Induced Resistance and Germicidal Effects

Abstract

<jats:p>Shortwave ultraviolet radiation (UV-C) was tested for controlling natural infections and inducing resistance to fungal decay caused by <jats:italic>Botrytis cinerea</jats:italic> Pers.: Fr. (gray mold rot) in bell pepper [<jats:italic>Capsicum annuum</jats:italic> L. var. <jats:italic>annuum</jats:italic> (Grossum Group)] fruit. All UV-C doses tested (0.22, 0.44, 0.88, or 2.20 kJ·m<jats:sup>-2</jats:sup>) caused a reduction in the number of natural infections occurring during storage at 13 °C. A UV-C dose of 0.88 kJ·m<jats:sup>-2</jats:sup> controlled most effectively natural infections in peppers stored at both 13 or 20 °C. Although UV-C was found to be highly germicidal to <jats:italic>B. cinerea</jats:italic> conidia exposed on agar or on fruit wounds, it did not prevent infection of fruit inoculated with the pathogen 24 hours before exposure to UV-C. However, fruit which were exposed to UV-C 24 hours before inoculation with <jats:italic>B. cinerea</jats:italic> had a lower percentage of infections. For this reason, UV-C appears to act mainly as an inducer of disease resistance in this crop rather than a sanitizing agent. UV-C was effective in inducing resistance to <jats:italic>B. cinerea</jats:italic> in fruit at various stages of maturity, from green to red. Disease resistance was also induced in fruit which had been stored for 7 days before UV-C treatment. The effect of UV-C doses was found to be additive as two successive exposures at 0.44 kJ·m<jats:sup>-2</jats:sup> had an equivalent effect as one exposure to the optimal dose of 0.88 kJ·m<jats:sup>-2</jats:sup>. However, two successive exposures to 0.88 kJ·m<jats:sup>-2</jats:sup> were less effective than one exposure to this dose.</jats:p>

Ultraviolet-C light inactivation of Penicillium expansum on fruit surfaces

“…Similar observations on the effectiveness of UV-C in reducing the microbial populations on food surfaces have been reported recently. UV-C with 2.2 and 4.4 kJ/m 2 intensity showed effectiveness in reducing the Botrytis cinerea population on bell peppers (Mercier, Baka, Reddy, Corcuff, & Arul, 2001). Syamaladevi et al (2014) reported 2.8 log reduction in P. expansum population on the pear surface after a UV-C dose of 1.7 kJ/m 2 .…”

Maize growth and developmental responses to temperature and ultraviolet-B radiation interaction

“…The squarewave supplementation systems were used to provide desired UV-B radiation doses which were delivered from 0.5 m above the plant canopy for 8 h, each day, from 8:00 to 16:00 h by 8 fluorescent UV-B-313 lamps (Q-Panel Company, Cleveland, OH, USA) mounted horizontally on a metal frame inside each SPAR chamber. To filter-out and avoid the germicidal effects of UV-C radiation (<280 nm) (Mercier et al 2001), the lamps were wrapped with presolarized (kept under UV-B light for 48 h to stabilize transmission) 0.07 mm cellulose diacetate (CA) film (JCS Industries Inc., La Mirada, CA, USA). The CA film was changed every 3-4 d to account for the degradation of CA properties.…”

Maintenance of fresh boysenberry fruit quality with UV-C light and heat treatments combined with low storage temperature

“…While artificial UV-C radiation also delays fruit ripening (Lu et al, 1991) and affects fruit softening (Ait Barka et al, 2000), literature on photochemical radiation with UV-C is primarily related to its germicidal activity and induction of disease resistance. The biological mechanisms by which such activity may take place include direct inactivation of conidia (Marquenie et al, 2002), elicitation of a wide array of compounds involved in defence responses, such as phytoalexins (Adrian et al, 2000;Ben-Yehoshua et al, 1992;Douillet-Breuil et al, 1999;Mercier et al, 1993Mercier et al, a, 1993Mercier et al, b, 2001, and accumulation of antifungal enzymes such as phenylalanine ammonia-lyase (Nigro et al, 1998(Nigro et al, , 2000, chitinase and β-1,3-glucanase (Porat et al, 1999). Many of these complex biochemical mechanisms involved in the induction of fruit resistance, such as preformed antifungals and pathogenesis-related proteins, are also elicited by heat treatments (Pavoncello et al, 2001).…”

“…It has been reported that heat treatment and UV-C light could help to reduce fruit damage and pathogen attack during storage (Paull, 1990;Lurie, 1998;Baka et al, 1999;Marquenie et al, 2002Marquenie et al, , 2003. The beneficial effects of these treatments are thought to be mediated by different processes including inactivation of pathogens (Fallik et al, 1995), production of phytoalexins (Adrian et al, 2000;Ben-Yehoshua et al, 1992;Douillet-Breuil et al, 1999;Mercier et al, 1993aMercier et al, , 1993bMercier et al, , 2001, induction of defensive enzymes like phenylalanine ammonia-lyase (Nigro et al, 1998(Nigro et al, , 2000, peroxidases (Lurie et al, 1997), chitinases and glucanases (Schirra et al, 2000), and delayed cell-wall degradation (Lurie, 1998;Ait Barka et al, 2000;Paull and Chen, 2000).…”