Light Activation of Russian Wheat Aphid-Elicited Physiological Responses in Susceptible Wheat

Abstract

The impact of light and its role in Russian wheat aphid, Diuraphis noxia (Mordvilko), damage symptom formation, and photosynthetic capacity in 'Arapahoe' wheat (Triticum aestivum L.) were examined. After 72 h under continuous dark or continuous light regimes, the number of aphids (nymphs), leaf rolling and chlorosis ratings, fresh leaf weight, and chlorophyll contents were recorded. Photosynthetic rates, chlorophyll a, kinetics and chlorophyll extractions also were determined. Aphid infestation caused significant reductions in plant height, fresh weight, gas exchange, and chlorophyll fluorescence only under continuous light. Under the 72 h continuous dark regime, aphid infestation did not cause either damage symptom formation or reduction in plant growth or metabolism (photosynthesis). Furthermore, significantly more D. noxia nymphs were produced under continuous light condition than continuous dark. Our results demonstrate that the development of D. noxia feeding damage symptoms (i.e., leaf rolling and chlorotic streaks) on susceptible wheat seedlings is a light-activated process, even though the elicitor of the plant damage symptoms is aphid feeding.

Physiological responses of wheat and barley to Russian wheat aphid, Diuraphis noxia (Mordvilko) and bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae)

“…Macedo et al (2003a) reported similar changes in qP and qN and suggested that biochemical mechanisms for restoring chlorophyll to a low energy, light receptive-state, such as quenching, may be more immediately impaired by aphid feeding.…”

“…After aphid removal, the tolerant cultivar demonstrated a complete recovery of photosynthetic capacity, while photosynthetic compensation did not occur in the susceptible or antibiotic cultivars. Macedo et al (2003a) also found that D. noxia infestation on susceptible wheat can cause significant reductions in gas-exchange and chlorophyll fluorescence, but only under continuous light. Aphid infestation under 72 h continuous dark was not associated with damage symptom formation or reduced photosynthetic metabolism.…”

“…Reductions in rubisco activity also can result from indirect effects, like end-product inhibition, rather than direct impairment of some feature of the photosynthetic carbon reduction cycle. End-product inhibition has been proposed as a cause for changes in photosynthesis arising from aphid injury (Macedo 2003).…”

Impact of <I>Diuraphis noxia</I> and <I>Rhopalosiphum padi</I> (Hemiptera: Aphididae) on Primary Physiology of Four Near-Isogenic Wheat Lines

“…The physiological and biochemical changes in wheat plants elicited by D. noxia feeding have been evaluated (Miller et al 1994;van der Westhuizen and Pretorius 1996;RaÞ et al 1996;Haile et al 1999;Ni et al 2001Ni et al , 2002Ni and Quisenberry 2003;Macedo et al 2003b). D. noxia usually feeds at the base of the youngest leaves of the plant, which is a strong sink for phloem-mobile mineral nutrients, amino compounds, and carbohydrates.…”

“…The duration of infestation might be intimately linked with the biochemical and physiological response of wheat plants (Kriel et al 1986, Aalbersberg et al 1989, Hein et al 1989, Hein 1992, Macedo et al 2003b). In addition, previous studies demonstrated that although the mechanical injury pattern of different aphid species, such as D. noxia and R. padi, seems to be very similar, the salivary components in these species vary in composition, particularly oxido-reductases (catalase and peroxidase), which perhaps has a key role on injury-symptom development (i.e., leaf chlorosis) .…”