Abstract
UV-B induced changes in plants can influence sap-feeding insects through mechanisms that have not been studied. Herein the grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), was monitored on barley plants under the treatments of control [0 kJ/ (m2.d)], ambient UV-B [60 kJ/ (m2.d)], and enhanced UV-B [120 kJ/ (m2.d)] irradiation. Electrical penetration graph (EPG) techniques were used to record aphid probing behaviors. Enhanced UV-B irradiated plants negatively affected probing behaviors of S. avenae compared with control plants. In particular, phloem factors that could diminish sieve element acceptance appeared to be involved, as reflected by smaller number of phloem phase, shorter phloem ingestion, and fewer aphids reaching the sustained phloem ingestion phase (E2>10min). On the other hand, factors from leaf surface, epidermis, and mesophyll cannot be excluded, as reflected by higher number of non-probing, longer non-probing and pathway phase, and later the time to first probe.
Highlights
Ultraviolet-B (UV-B) is a very narrow band at the short wavelength (280-315nm) end of the daylight spectrum
Nested ANOVA tests revealed that there were no significant differences among the subgroups for the number of non-probing (n_Np), sum of non-probing phase (s_Np), time to first probe (t > 1Pr), sum of the pathway phase (s_C), and time to first phloem phase in experiment (t >1E), but there were significant differences among UV-B treatments for those variables (Table 1)
The number of phloem phase (n_E), s_E2 were significantly decreased for S. avenae fed on enhanced UV-B plants compared to those fed on the control or ambient UV-B plants (n_E: 2.644±0.16 vs 3.96±0.19 or 3.75±0.18; s_E2: 86.75±5.12 min vs 157.13±20.34 min or 108.51±5.16 min; Tukey’s HSD, P
Summary
Ultraviolet-B (UV-B) is a very narrow band at the short wavelength (280-315nm) end of the daylight spectrum. Due to the human-induced destruction of the UV-B-absorbing stratospheric layer of ozone, the amount of UV-B radiation reaching the surface of the earth has increased during the last two decades (Björn et al, 1998; Randel et al, 1999). This has led to concerns about potential biological impacts on the environment (Madronich et al, 1998; McCloud and Berenbaum, 1999). Changes in plant morphology and physiology in response to UV-B exposure are numerous. UV-B can affect the cuticle compositions, phytohormone levels, proteinase inhibitor activities, as well as levels of many secondary plant metabolites to varying extents (Kuhlmann and Muller, 2011)
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