  We investigate the impact of the recently released FNAL-E906 (SeaQuest) data
on the ratio of proton-deuteron and proton-proton Drell-Yan production
cross-sections on the sea quark PDFs. We find that they have constraining power
on the light-quark sea isospin asymmetry $(\bar{d}-\bar{u})(x)$ and on the
$(\bar{d}/\bar{u})(x)$ ratio at large longitudinal momentum fraction $x$
values, and that their constraints turn out to be compatible with those from
Drell-Yan data in collider experiments (Tevatron and Large Hadron Collider) and
in the old fixed-target experiment by the FNAL-E866 collaboration. We study the
impact of nuclear corrections due to the deuteron target, finding them within
1% in most of the kinematic region covered by SeaQuest. We perform a new proton
PDF fit, including SeaQuest data, using the ABMP16 methodology and we compare
it to the ABMP16 baseline.
