Physiological responses of resistant and susceptible barley, Hordeum vulgare to the Russian wheat aphid, Diurpahis noxia (Mordvilko)

Abstract

Knowledge of the physiological responses of barley, Hordeum vulgare L., to the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Hemiptera: Aphididae) is critical to understanding the defense response of barley to aphid injury and identifying resistance mechanisms. This study documented the impact of D. noxia feeding on resistant ('Sidney') and susceptible ('Otis') barley through chlorophyll fluorescence measurements, chlorophyll content, and carbon assimilation (A-C i ) curves recorded at 1, 3, 6, 10, and 13 days after aphid introduction. All chlorophyll fluorescence parameters evaluated were similar between aphid-infested and control plants for both cultivars. A-C i curves showed that D. noxia feeding negatively impacts the photosynthetic capacity in both cultivars, but this effect was greater in the susceptible plants. From the A-C i curves, it is apparent that compensation occurs in resistant barley by day 10, but by the conclusion of the experiment, aphid populations reached levels that overwhelmed the resistant barley seedlings. Differences observed in carbon assimilation curves between control and infested plants show that D. noxia feeding impacts the dark reaction, specifically rubisco activity and RuBP regeneration. It is likely that declines in the photochemical efficiency and chlorophyll content of the plants may be a secondary effect and not the primary trigger of declines in host plant function.

Plant responses to insect herbivory: interactions between photosynthesis, reactive oxygen species and hormonal signalling pathways

“…The hypothesis that insect‐induced changes in photosynthesis are genetically programmed is supported by the observation that plant genotypes that are able to maintain photosynthesis under insect attack often exhibit greater resistance. Infestation of barley (Gutsche et al . 2009a) and wheat (Haile et al .…”

“…There is also accumulating evidence to suggest that reduced photosynthesis is a genetically programmed plant response. Gas exchange measurements coupled with fluorescence techniques have demonstrated that at least in certain plant-insect interactions repressed photosynthetic rates result not from impaired CO2 availability or impairment of the light reaction but to reduced rates of CO2 fixation within the dark reaction (Peterson et al 1998;Macedo et al 2005;Gutsche et al 2009a). This suggests that limitation is associated with either ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity or the regeneration of ribulose bisphosphate, which is dependent on enzymes and metabolites of the photosynthetic carbon reduction cycle.…”

“…The hypothesis that insect-induced changes in photosynthesis are genetically programmed is supported by the observation that plant genotypes that are able to maintain photosynthesis under insect attack often exhibit greater resistance. Infestation of barley (Gutsche et al 2009a) and wheat (Haile et al 1999;Franzen et al 2007) by the economically significant Russian wheat aphid (Diurpahis noxia) revealed that tolerant lines were able to maintain photosynthetic capacity more strongly during insect feeding or were able to recover photosynthetic rates more rapidly following removal of aphids. Crucially, the rate of ribulose bisphosphate turnover (as estimated from gas exchange measurements) was maintained in resistant but not in susceptible cultivars (Franzen et al 2007;Gutsche et al 2009a).…”

Transcriptional Profiling of Resistant and Susceptible Buffalograsses in Response to Blissus occiduus (Hemiptera: Blissidae) Feeding

“…GST production has been documented in response to both abiotic and biotic stresses (Dixon et al 2002). Expression of specific GST transcripts has been documented in resistant barley as well as resistant sorghum in response to aphid feeding, further implicating the potential role of GST in the plant defense response to insect pressure (Park et al 2005, Gutsche et al 2009a.…”

“…These plant-signaling pathways are most commonly mediated by a number of different compounds including jasmonic acid, salicylic acid, and ethylene (Walling 2000, Thompson andGoggin 2006). Prior research has documented differential expression of transcripts between resistant and susceptible plants involved in oxidative burst, plant defense and signaling, photosynthesis, and cell maintenance in response to phloem-feeding insects (Zhang et al 2004, Park et al 2005, Botha et al 2006, Boyko et al 2006, Gutsche et al 2009a). Understanding tolerance mechanisms at a molecular level will provide insights into the biological pathways impacted by chinch bug feeding and help illuminate plant tolerance mechanisms.…”