MONSANTO TO BAR A CLASS OF SEEDS
Monsanto Co, lightning rod for furor over so-called 'Terminator' technology that uses genetic modifications to create plants able to resist insect pests and weed killers, seeks to remove itself from inflamed debate over biotechnology; will make no further efforts to market seeds that produce crop plants that are infertile; critics say genetic modification represents drive by agribusiness to make farmers dependent on them and chemicals many of them use; note seeds from engineered crops cannot be replanted, forcing farmers to buy new seeds year after year, rather than saving seeds from normal crops for replanting following spring; suggest pollen from engineered crops could render plants in neighbors' fields sterile without farmers realizing it; hail company's decision (M)