Actinidia seed-borne latent virus (ASbLV, Betaflexiviridae) is transmitted paternally and maternally at high rates

Abstract

Actinidia seed-borne latent virus (ASbLV, Betaflexiviridae, genus Prunevirus) was detected at high frequency in healthy seedlings grown from lines of imported seed in a New Zealand post-entry quarantine facility. To determine the route and efficiency of transmission of ASbLV in this dioecious crop species, we developed a rapid molecular protocol and identified a reliable progeny plant tissue to determine paternal and maternal transmission rates. The virus was detected at a high incidence (98%) in individual seeds, but cotyledon testing of seedlings from selected crosses confirmed staminate (male) transmission at high frequency (~ 60%), and pistillate (female) transmission at even higher frequency (~ 80%). The use of cotyledons allows non-destructive detection of ASbLV in very young seedlings that enables early screening of kiwifruit plants in nurseries to manage its spread to orchards. The high ASbLV transmission rates, whether from infected pollen or ovules, facilitate bulk testing of seed lots that could quickly detect infected parent plants (fruit bearing female or male pollinator) already in an orchard. The dioecious nature of Actinidia may provide a useful biological tool to further investigate ASbLV movement, transmission biology, and ultimately its impact on infected Actinidia plants.