Effect of Lupin Cyclitols on Pea Aphid Probing Behaviour

Abstract

Effect of Lupin Cyclitols on Pea Aphid Probing BehaviourThe cyclitols: D-pinitol, D-chiro-inositol are naturally present in the tissues ofLupinus angustifolius. The effect of these cyclitols on the behaviour of the pea associated clone ofAcyrthosiphon pisumduring various stages of probing was studied. The main stage of probing studied was the stylet penetration in mesphyll and vascular bundle. D-pinitol, D-chiro-inositol and their mixture were exogenously applied to peaPisum sativumexplants and the aphid probing behaviour was evaluated using the Electrical Penetration Graph technique (EPG). Feeding of peas with cyclitols at a concentration of 10 mM, caused a selective accumulation of D-pinitol and D-chiro-inositol in stems, leaf petioles, and leaf blades. In aphid bodies, both cyclitols were traced, respectively, to the host plant treatment. The new cyclitols in pea tissues did not significantly affect the total duration and frequency of aphid activities during probing in peripheral as well as vascular tissues. However, the aphid behaviour on cyclitol-treated plants as compared to their behaviour on the control was slightly altered. Non-probing and probing in mesophyl prevailed among aphid activities during the initial period of stylet penetration. Aphids on D-pinitol+D-chiro-inositol-treated plants reached phloem vessels relatively later than aphids on the control and D-chiro-inositol plants. There were recurrent switches between E1 (salivation) and E2 (sap ingestion) patterns in some aphids during the phloem phase on D-pinitol and D-pinitol+D-chiro-inositol - treated plants. This may reflect difficulties in the uptake of the phloem sap, and point to lupin cyclitols as being responsible, at least in part, for the rejection ofL. angustifoliusas a host plant by the pea clone ofA. pisum.