Trasmissione dei fitovirus e possibile trasmissibilità dei fitoplasmi attraverso il seme: fatti, fattori e meccanismi.

Seed transmission of viruses and phytoplasmas: facts, factors and mechanisms. An account is given of the mechanism(s) involved in the seed transmission of plant viruses, most of which have been elucidated only recently and in few instances. Evidence has been provided that seed transmission by direct invasion of the embryo via the ovule depends upon symplastic transport of the virus from infected maternal cells. Such transport pathways have not been identified in higher plants but it has been shown that symplastic connections at the testa-boundary wall as well as porelike structures at the endosperm–suspensor boundary do exist in virus-infected plants. The role of virus determinants like the suppressors of posttranscriptional gene silencing in seed transmission is also discussed. Control measures to limit seed transmission capitalize on the availability of sensitive, reliable and labour saving immunological and nucleic acid-based laboratory techniques however emphasis is placed on the risk of sample contamination in doing these tests. Finally, some preliminary results suggest that also phytoplasmas agents of plant diseases could be transmitted through seeds, posing the needs for a more accurate investigation.