FURTHER EVIDENCE OF DURABLE RESISTANCE IN HONEYSWEET TRANSGENIC PLUM UNDER NATURAL INFECTION WITH D AND REC STRAINS OF PLUM POX VIRUS.

'HoneySweet' is a transgenic plum protected against Plum pox virus (PPV). Its behaviour to natural PPV infection was the subject of different field trials undertaken in several endemic European countries. The first experiment in Romania was performed between 1996-2006 and no 'HoneySweet' tree was found infected under high natural PPV infection pressure. To further asses the durability of resistance to PPV of 'HoneySweet', a new field trial was established in 2013. As inoculum sources of PPV were used plants, previously artificially inoculated with D or Rec strains, grown in pots and placed inside of the blocks. Limited treatments with insecticides were made within the plot in order to stimulate the virus spread by aphids. The monitoring of PPV spreading was made by serological and molecular assays. Strains discrimination was made by RT-PCR. The temporal spread of PPV revealed a continual evolution of infection in conventional plums. No trees of transgenic plum 'HoneySweet' expressed PPV symptoms or were found infected, by serological and molecular assays, confirming its durable resistance to natural PPV infection with D or Rec strains. [ABSTRACT FROM AUTHOR]