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Pollen Transmission of Asparagus virus 2 (AV-2) May Facilitate Mixed Infection by Two AV-2 Isolates in Asparagus Plants

September 2014 , Volume 104 , Number  9
Pages  1,001 - 1,006

Ryusuke Kawamura, Hanako Shimura, Tomofumi Mochizuki, Satoshi T. Ohki, and Chikara Masuta

First, second, and fifth authors: Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan; and third and fourth authors: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan.

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Accepted for publication 5 February 2014.

Asparagus virus 2 (AV-2) is a member of the genus Ilarvirus and thought to induce the asparagus decline syndrome. AV-2 is known to be transmitted by seed, and the possibility of pollen transmission was proposed 25 years ago but not verified. In AV-2 sequence analyses, we have unexpectedly found mixed infection by two distinct AV-2 isolates in two asparagus plants. Because mixed infections by two related viruses are normally prevented by cross protection, we suspected that pollen transmission of AV-2 is involved in mixed infection. Immunohistochemical analyses and in situ hybridization using AV-2-infected tobacco plants revealed that AV-2 was localized in the meristem and associated with pollen grains. To experimentally produce a mixed infection via pollen transmission, two Nicotiana benthamiana plants that were infected with each of two AV-2 isolates were crossed. Derived cleaved-amplified polymorphic sequence analysis identified each AV-2 isolate in the progeny seedlings, suggesting that pollen transmission could indeed result in a mixed infection, at least in N. benthamiana.

© 2014 The American Phytopathological Society