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

• Main Authors: Jaime Jiménez, Aránzazu Moreno, Alberto Fereres
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Viruses
• Subjects: <i>Beet yellows virus</i>; <i>Myzus persicae</i>; <i>Closterovirus</i>; phloem-pd; electrical penetration graphs
• Online Access: https://www.mdpi.com/1999-4915/13/1/137

The green peach aphid <i>Myzus persicae</i> Sulzer is the main vector of the semipersistently transmitted and phloem-limited <i>Beet yellows virus</i> (BYV, <i>Closterovirus</i>). Studies monitoring the <i>M. persicae</i> 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 <i>M. persicae</i> 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.