Rust is a devastating fungal disease that afflicts many crops from corn to soybeans. Pictured here erupting from beneath the soy plant's skin, the fungus can destroy as much as 80 percent of a harvest. Resistance to rust is a major focus for plant breeders and companies working on genetically modified strains. The goal: to strengthen plant cell walls to resist the fungal invader or to program infected cells to kill themselves and limit damage to plant leaves.