Agronomy (Nov 2022)

Ultraviolet-B Irradiation Induces Resistance against Powdery Mildew in Cucumber (<i>Cucumis sativus</i> L.) through a Different Mechanism Than That of Heat Shock-Induced Resistance

  • Dinar Mindrati Fardhani,
  • Agung Dian Kharisma,
  • Tomoyuki Kobayashi,
  • Nur Akbar Arofatullah,
  • Makoto Yamada,
  • Sayuri Tanabata,
  • Yumi Yokoda,
  • Ani Widiastuti,
  • Tatsuo Sato

DOI
https://doi.org/10.3390/agronomy12123011
Journal volume & issue
Vol. 12, no. 12
p. 3011

Abstract

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Heat shock treatment (HST) and UV-B irradiation can reduce pathogen infection in crops. However, information on the mechanism of UV-B action is limited. Here, we investigated the mechanism of UV-B-induced resistance against powdery mildew in cucumber and compared it to that of heat-shock-induced resistance. We measured the percentage of leaf area showing disease symptoms and examined the expression levels of defense- and heat-shock-related genes across treatment groups. UV-B irradiation (intensity, 5 µW/cm2) for 4 h/d followed by pathogen inoculation reduced the appearance of powdery mildew by 21.17% compared with the control group. Unlike HST—which induces systemic resistance—UV-B irradiation induced local resistance in cucumber, as indicated by local changes in gene expression (Chi2 and ETR2). UV-B-treated plants inoculated with powdery mildew showed higher expression levels of Chi2, ETR2, and LOX6 than plants that were either treated with UV-B or inoculated. UV-B had no major effects on systemic acquired resistance or heat shock transcription factors, which are known to be affected by HST. Combined HST and UV-B had a strong synergistic effect in reducing powdery mildew in cucumber. Our results indicate that UV-B treatment likely operates through a different mechanism than HST in triggering cucumber resistance against powdery mildew infection.

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