Vol.:(0123456789) 1 3 Arthropod-Plant Interactions https://doi.org/10.1007/s11829-019-09708-w ORIGINAL PAPER The phloem‑pd: a distinctive brief sieve element stylet puncture prior to sieve element phase of aphid feeding behavior J. Jiménez 1,2  · E. Garzo 1  · J. Alba‑Tercedor 3  · A. Moreno 1  · A. Fereres 1  · G. P. Walker 4 Received: 11 January 2019 / Accepted: 19 July 2019 © Springer Nature B.V. 2019 Abstract A recent electrical penetration graph (EPG) study identifed a unique intracellular puncture that is associated with inoculation of the semipersistently transmitted, phloem-limited Beet yellows virus (BYV, Closterovirus) by the aphid Myzus persicae. This new aphid EPG pattern (named phloem-pd) always occurs shortly before phloem sieve element phase (PSEP) and has a similar voltage drop as PSEP, both of which are less than the voltage drop of standard-pds. Structure of pd subphase II-2 difers between phloem-pds and standard-pds. The objective of this study was to determine the type of phloem cell penetrated during phloem-pds. Stylets of M. persicae feeding on sugar beet (Beta vulgaris) were fxed in situ by cryofxation during phloem-pds, standard-pds and PSEP waveform E1. The cell penetrated by the stylet tips was then identifed by confocal laser- scanning microscopy and micro-computed tomography. Sieve elements (SEs) or companion cells (CCs) were penetrated dur- ing phloem-pds, whereas cells other than SEs or CCs (mesophyll, bundle sheath cells and possibly phloem parenchyma) were penetrated during standard-pds. SEs were penetrated during waveform E1. The implications of these fndings for inoculation of other phloem-limited viruses that currently are thought to be inoculated primarily during waveform E1 are discussed. Keywords Confocal laser-scanning microscopy · Electrical penetration graphs · Micro-computed tomography · Plant virus inoculation Introduction Many plant viruses require insect vectors to be transmitted from infected plants to new uninfected host plants (Fereres and Raccah 2015). Therefore, the study of insect feeding activities in the plant and their relationship to virus acquisi- tion and inoculation enhances our understanding of virus epidemiology and may contribute to developing strategies for controlling the spread of plant viruses. Numerous studies Handling Editor: Robert Glinwood. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11829-019-09708-w) contains supplementary material, which is available to authorized users. * A. Fereres a.fereres@csic.es J. Jiménez jaimejimenez@ica.csic.es E. Garzo elisa.garzo@ica.csic.es J. Alba-Tercedor jalba@ugr.es A. Moreno amoreno@ica.csic.es G. P. Walker walker@ucr.edu 1 Instituto de Ciencias Agrarias – Consejo Superior de Investigaciones Científcas (ICA-CSIC), C/Serrano 115 dpdo, 28006 Madrid, Spain 2 Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas (ETSIAAB), Universidad Politécnica de Madrid (UPM), Madrid, Spain 3 Departamento de Zoología – Facultad de Ciencias, Universidad de Granada, Campus de Fuentenueva, 18071 Granada, Spain 4 Department of Entomology, University of California, Riverside, CA 92521, USA