The hundred or so farmers crowding the ballroom of the Mendenhall Inn in Chester County, Pennsylvania, might not have had a background in gene editing, but they knew mushrooms. These local growers produce a staggering 1.1 million pounds of mushrooms on average every day, which is one reason Pennsylvania dominates the annual $1.2-billion U.S. market. Some of the mushrooms they produce, however, turn brown and decay on store shelves; if you've ever held a slimy, decomposing, formerly white mushroom in your hand, you know why no ones buys them. Mushrooms are so sensitive to physical insult that even careful “one-touch” picking and packing can activate an enzyme that hastens their decay.