The question of seed transmissibility of Plum pox virus

Abstract

For many years, Plum pox virus (PPV) was considered to be transmissible by seed, increasing the fear of long-distance spread of the disease. In the late 1970s, it was claimed on the basis of biological transmission of the virus to herbaceous indicator plants and the development of serological diagnosis based on polyclonal antibodies, that PPV was seed-transmitted, with a different infection rate according to the plant species and part of the seed which was tested. In the 1990s, PPV was characterized into four different types, and specific monoclonal antibodies were produced for them. These new and more sensitive diagnostic techniques, together with RT-PCR with different sets of specific primers, were used to approach once again the problem of PPV transmission through seeds. The virus was detected in seed coats and cotyledons, but embryonic tissue and seedlings obtained from germinated seeds never showed symptoms, and gave negative results for PPV with both ELISA and PCR assays. No PPV isolate is currently recognized to be seed transmitted, so vertical transmission of PPV from infected mother plants to their progeny does not occur. Hypothetically, the only possibility of seed transmission would arise from a mutation in the helper component of the virus, associated with high susceptibility of the infected Prunus cultivar.

Vertical transmission of Prunus necrotic ringspot virus: hitch-hiking from gametes to seedling

“…In our study, PNRSV invaded both the embryo and cotyledons (Figs 3c and 4a, b). It seems that infection of the embryo is a prerequisite for seed transmission, given that other viruses that are able to infect only the cotyledons are not seed-transmitted, as in the case of plum pox virus (Pasquini & Barba, 2006).…”

Unfolding the secrets of plum pox virus: from epidemiology to genomics

“…As these serotypes were found to be vastly prevalent in Europe, PPV variability has been considered to be very low for a long time (Revers et al, 1996). While the PPV-D isolates have been found mainly in plums and apricots , PPV-M has been linked to the severe epidemics of peaches (Pasquini and Barba, 1997), leading to a narrowing generalization of the strain properties.…”

No Seed Transmission of Plum Pox Virus in Japanese Apricot

“…The term "seed transmission" should entail the transmission of a virus to progenies through seeds, not the transmission from parental reproductive tissues to seed tissues. Some positive results in older reports including one by Szirmai (1961) should be questioned due to the lack of a vector control in the seedlings tested (Pasquini & Barba 2006). Pasquini and Barba (2006) cited two early works by Coman and Cociu (1976) and Sǎvulescu and Macovei (1965) that did find seed transmission in plums and peaches, respectively.…”

“…Some positive results in older reports including one by Szirmai (1961) should be questioned due to the lack of a vector control in the seedlings tested (Pasquini & Barba 2006). Pasquini and Barba (2006) cited two early works by Coman and Cociu (1976) and Sǎvulescu and Macovei (1965) that did find seed transmission in plums and peaches, respectively. However, these manuscripts were not available to the authors, making it difficult to evaluate the technical plausibility of these works.…”

“…The transmissibility of PPV through seeds has already been studied in many countries, but unfortunately with conflicting results (Pasquini & Barba 2006). If PPV is truly transmitted by seeds, then fruits and seeds may play an important role in long-distance dissemination, in which case the control of fruits and seeds through plant quarantines would be fully justified.…”