Abstract
UV-C irradiation is known to enhance plant resistance against insect pests. In the present study, we evaluated the effects of low doses of UV-C on Macrosiphum rosae infesting greenhouse rose (Rosa x hybrida) plants. The application of 2.5-kJ/m2 UV-C irradiation on rose leaves before infestation induced anti-herbivore resistance and negatively affected the aphid fecundity. No eggs and first instar nymphs were recorded on irradiated leaves, whereas an average of 4.3 and 2.7 eggs and 6.7 and 14 first instars were recorded on vars. “Etoile Brilante” and “Arlen Francis” untreated leaves, respectively. UV-C irradiation reduced the aphid population from naturally infested rose plants by up to 58%. In a greenhouse pot trial (GPT) in 2019, UV-C irradiation minimised the initial aphid population six hours after treatment. UV-C elicited host resistance and, also, helped in aphid repulsion without killing the adult individuals. UV-C did not affect the physiological responses of rose plants. The net CO2 assimilation of the UV-C irradiated plants ranged between 10.55 and 15.21 μmol/m2. sec for “Arlen Francis” and between 10.51 and 13.75 μmol/m2. sec for “Etoile Brilante” plants. These values, with only a few exceptions, were similar to those recorded to the untreated plants.
Highlights
UV irradiation is the spectrum of light from 100 to 400 nm (UV-C = 100–280 nm, UV-B = 280–315 nm and UV-A = 315–400 nm)
The treatment of plants with UV has been associated with the potential induction of the phenylpropanoid pathway, leading to the formation of flavonoids, isoflavonoids, coumarins, soluble esters, wall-bound phenolics, lignin and suberin [1,2] UV-B irradiation applied to field-grown Nicotiana longiflora plants induced the same regulatory defence responses to those induced after caterpillar attacks [3]
The 1st instar aphid population was negatively affected by UV-C irradiation
Summary
The treatment of plants with UV has been associated with the potential induction of the phenylpropanoid pathway, leading to the formation of flavonoids, isoflavonoids, coumarins, soluble esters, wall-bound phenolics, lignin and suberin [1,2] UV-B irradiation applied to field-grown Nicotiana longiflora plants induced the same regulatory defence responses to those induced after caterpillar attacks [3]. It was suggested that UV-B and chewing insects activated common regulatory elements, and plants exposed to solar UV-B irradiation expressed increased resistance, compared to plants grown in the absence of UV-B. Defence responses against herbivores include the production of jasmonates, which regulate similar gene expression with that during herbivore attack, leading to induced herbivore resistance responses [4,5,6].
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