Nutritional quality of phloem sap in relation to host plant-alternation in the bird cherry-oat aphid

Abstract

Host alternation in aphids has been attributed to complementary growth of host plants, or more specifically to seasonal changes in the nitrogen quality of the phloem sap. In this report, seasonal fluctuation of free amino acids in phloem of the winter and summer host plants (Prunus padus, bird cherry and Hordeum 6ulgare, barley) of Rhopalosiphum padi (the bird cherry-oat aphid) were investigated in the context of aphid growth and behaviour. Phloem was collected from the cut stylets of aphids taken from plants that were grown outdoors. The total concentration of amino acids in P. padus phloem increased between bud break and late flush (spring), decreased in mature leaves (summer), and increased again in early senescent leaves (autumn). In H. 6ulgare, however, amino acid concentration fluctuated less from seedlings to flowering. Spring aphids from P. padus grew rapidly on this host from bud break to late flush, but died on mature and early senescent leaves. Summer aphids from H. 6ulgare grew as fast on this host as spring aphids did on flush leaves of P. padus. Sexual females grew more slowly than other generations and nearly as well on mature as on early senescent P. padus leaves. As judged by aphid growth and phloem nitrogen quality, P. padus during spring equals the summer host H. 6ulgare. However, the lower growth rates of R. padi on mature and senescent leaves of P. padus appear only loosely correlated with phloem amino acid concentrations. Therefore, factors influencing aphid nutrition, or ecology, other than seasonal changes in phloem sap amino acid concentration may explain the existence of host alternation in R. padi.

Probing behavior of bird cherry-oat aphid Rhopalosiphum padi (L.) on native bird cherry Prunus padus L. and alien invasive black cherry Prunus serotina Erhr. in Europe and the role of cyanogenic glycosides

“…This signal may act as early as at the time of aphid emergence in spring. As it was shown by Sandström (2000), factors influencing aphid nutrition, or ecology, other than seasonal changes in the nutritional value of the phloem sap may play a role in the phenomenon of host alternation in R. padi. Nevertheless, a detailed study on the seasonal and phenological changes in plant secondary chemistry is planned to clarify the role of cyanogenic glycosides in host selection by R. padi more precisely.…”

Effect of host plant alternation on some adaptive enzymes of the bird cherry–oat aphid, Rhopalosiphum padi (L.)

“…Aphid migration between the two species of host plant requires winged morphs that are produced in response to changes in quality of host plant (Sandström 2000;Müller et al2001;Leszczynski et al 2003). In the case of the bird cherry-oat aphid, winged morphs stop feeding on the primary host directly before migration (Leszczynski et al 1998).…”

“…By the second day of adult life, 87% of R. padi migrants left the bird cherry leaves and did not return to the winter host (Glinwood and Pettersson 2000). Migration from the primary to the secondary host might result from the decrease of nutritional quality of mature leaves of the bird cherry or from the accumulation of plant allelochemicals in the bird cherry tissues (Sandström 2000;Gukasik et al 2001). The changes in activity of the enzymes within the migrant tissues after colonisation of the summer host may be interpreted as biochemical adaptations of the bird cherry-oat aphid to distantly related host plants diVering in chemical composition.…”

“…The Wrst, called fundatrix specialisation, proposes that host alternation is maladaptive and results from the morph that hatches from the winter egg being highly specialised for feeding on the primary host and being unable to feed on the secondary host (Moran 1992). The second hypothesis explains host alternation as a way to exploit the complementary growth patterns of woody and herbaceous plants (Sandström 2000). There are experimental data supporting both hypotheses, but little is known about the biochemical adaptations of bird cherry-oat aphids during host alternation.…”

Loss of Resistance to <i>Nilaparvata lugens</i> May Be Due to the Low-Level Expression of <i>BPH32 </i>in Rice Panicles at the Heading Stage

“…The mechanism of plant resistance to phloem sap-feeding insects has been reported to involve the balance of the amino acid composition of the phloem sap [12] [13]. The remobilization of nitrogen in the rice panicles can increase the total free amino acids in the phloem sap [14] [15], which may affect BPH resistance.…”