New major food crops developed in recent times are:
few
many
some
none

I would say major new food crops are probably few although ongoing research such as at Agriculture and Agri-Food Canada has developed 14 new varieties of cereal recently as a small example so this is promising for the future especially since by 2050 the world's population is projected to reach over 9 billion people so food production needs to keep pace with such a high figure.