Further studies on the non-transmission of plum pox potyvirus by pollen and seed
Seed and pollen transmission of plum pox potyvirus (EPPO A2 quarantine pest) has been reexamined in Italy, on two highly susceptible apricot cultivars (cvs. Tonda di Costigliole and Bulida). It must be noted that contrasting results have been obtained in this field, as Németh and Kölber (1982) found seed transmission of the virus in some apricot, peach and plum cultivars and other researchers did not find such transmission. ELISA and immunosorbent electron microscopy plus decoration (ISEM-D) were used to detect plum pox potyvirus (PPV) in various apricot tissues. Results of pollen transmission studies showed that pollen collected from infected flowers did not carry the virus, and that it was not able to transmit PPV to seeds and leaves of cross-pollinated plants. In seed transmission studies, it was found that the virus could be detected in mature seeds showing typical symptoms on the stone. In these mature seeds, the virus was observed as short particle fragments and could be detected mainly in the seed coat (the virus was detected only in 1% of cotyledons from cv. Bulida and was not detected in cotyledons from cv. Tonda di Cotigliole). It was nevertheless observed that immature seeds contained intact particles. During seed germination, further degradation of the virus occurred, and in the germinated seeds PPV could no longer be detected. All seedlings grown from infected seeds gave negative results when tested by ELISA over three consecutive years and showed no symptoms on the leaves. The authors felt that there may be two mechanisms of exclusion of PPV from apricot seedlings. Firstly, in almost all cotyledons of infected seeds, PPV could not be detected, and secondly, intact virus particles present in immature seeds are then degraded during germination. In conclusion, these recent studies show that PPV is neither seed nor pollen-transmitted.
Eynard, A.; Roggero, P.; Lenzi, R.; Conti, M., Milne, R.G. (1991) Test for pollen and seed transmission of plum pox virus (Sharka) in two apricot cultivars.
Advances in Horticultural Science, 5(3), 104-106.
Németh, M.; Kölber, M. (1982) Additional evidence on seed transmission of plum pox virus in apricot, peach and plum proved by ELISA.
Acta Horticulturae, 130, 293-300.