Semipersistently Transmitted, Phloem Limited Plant Viruses Are Inoculated during the First Subphase of Intracellular Stylet Penetrations in Phloem Cells.

Jaime Jiménez,Aránzazu Moreno,Alberto Fereres

doi:10.3390/v13010137

Jaime Jiménez, Aránzazu Moreno + Show 1 more

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https://doi.org/10.3390/v13010137

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Abstract

The green peach aphid Myzus persicae Sulzer is the main vector of the semipersistently transmitted and phloem-limited Beet yellows virus (BYV, Closterovirus). Studies monitoring the M. persicae probing behavior by using the Electrical penetration graphs (EPG) technique revealed that inoculation of BYV occurs during unique brief intracellular punctures (phloem-pds) produced in companion and/or sieve element cells. Intracellular stylet punctures (or pds) are subdivided in three subphases (II-1, II-2 and II-3), which have been related to the delivery or uptake of non-phloem limited viruses transmitted in a non-persistent or semipersistent manner. As opposed to non-phloem limited viruses, the specific pd subphase(s) involved in the successful delivery of phloem limited viruses by aphids remain unknown. Therefore, we monitored the feeding process of BYV-carrying M. persicae individuals in sugar beet plants by the EPG technique and the feeding process was artificially terminated at each phloem-pd subphase. Results revealed that aphids that only performed the subphase II-1 of the phloem-pd transmitted BYV at similar efficiency than those allowed to perform subphase II-2 or the complete phloem-pd. This result suggests that BYV inoculation occurs during the first subphase of the phloem-pd. The specific transmission mechanisms involved in BYV delivery in phloem cells are discussed.

Highlights

Aphids are the major vectors of noncirculatively (NC) transmitted viruses, a virus category characterized by no latent period and loss after molting [1]
electrical penetration graph (EPG)-assisted transmission experiments showed that BYV transmission occurred from the onset of the phloem-pd produced by M. persicae
Aphids transmitted BYV at an efficiency of 56% (9/16) on recordings interrupted during the subphase II-1 of the phloem pd, with no significant differences with BYV transmission efficiency obtained after the interruption of the phloem-pd during the subphase II-2 (71%; 10/14) or after a complete phloem-pd (69%; 11/16) (Table 1)

Summary

Introduction

Aphids are the major vectors of noncirculatively (NC) transmitted viruses, a virus category characterized by no latent period and loss after molting [1]. Since the pioneer study conducted by [3], numerous studies have focused on the feeding behavior activities of sap-sucking insects associated with virus transmission. The electrical penetration graph (EPG) technique [4] has been key in the study of different aphid stylet activities involved in the transmission of plant viruses [5,6]. The different aphid stylet activities in plants have been correlated with several characteristic EPG patterns. The dominant EPG waveform during pathway phase is waveform C, which is correlated with the intercellular stylet pathway periodically interrupted by brief intracellular punctures that are identified in EPG recordings as potential drops (‘pds’) [7]

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