Trans-grafting could be a strategy to transfer virus resistance from a
transgenic rootstock to a wild type scion. However contradictory results
have been obtained in herbaceous and woody plants. This work was
intended to determine if the resistance to sharka could be transferred
from transgenic plum rootstocks to wild-type apricot scions grafted onto
them. To this end, we conducted grafting experiments of wild- type
apricots onto plum plants transformed with a construction codifying a
hairpin RNA designed to silence the PPV virus and studied if the
resistance was transmitted from the rootstock to the scion. Our data
support that the RNA-silencing-based PPV resistance can be transmitted
from PPV-resistant plum rootstocks to non-transgenic apricot scions and
that its efficiency is augmented after successive growth cycles. PPV
resistance conferred by the rootstocks was robust, already occurring
within the same growing cycle and maintained in successive evaluation
cycles. The RNA silencing mechanism reduces the virus titer
progressively eliminating the virus from the wild type scions grafted on
the transgenic resistant PPV plants. There was a preferential
accumulation of the 24nt siRNAs in the scions grafted onto resistant
rootstocks that was not found in the scions grafted on the susceptible
rootstock. This was coupled with a significant lower quantification of
the hpRNA in the resistant than in the susceptible or tolerant
rootstocks. Using transgenic rootstocks should mitigate public concerns
about transgenes dispersion and eating transgenic food and allow
conferring virus resistance to recalcitrant to transformation cultivars
or species.