According to Maule and Wang (1996), embryo infection can
occur by two routes, either directly from infected gametes at
fertilization or by direct invasion of the immature embryo from
virus-infected testa tissues. Wang and Maule (1994), working on
seed transmission of pea seed-borne mosaic virus, proposed that
transmission occurred by the virus using the embryonic suspensor,
as a conduit from the micropylar region of the embryo sac, to infect
the tip of the embryonic radicle, and that this route was closed by
degeneration of the suspensor.