Tests Show U.S. Failure to Block Contamination From Gene-Altered Varieties Much of the U.S. supply of ordinary crop seeds has become contaminated with strands of engineered DNA, suggesting that current methods for segregating gene-altered seed plants from traditional varieties are failing, according to a pilot study released yesterday. More than two-thirds of 36 conventional corn, soy and canola seed batches contained traces of DNA from genetically engineered crop varieties in lab tests commissioned by the Union of Concerned Scientists, a Washington-based advocacy group. The actual amount of foreign DNA present in U.S. seeds appears to be small, and most engineered...