For the first time, scientists claim to have made a genetic map of how a plant and a fungus live in a symbiotic relationship - and also found how fragile this relationship is. An international team, led by Massey University, has uncovered the complete set of gene messages which define the symbiotic interaction between a fungal endophyte and its grass host, a finding that may have implications for future research into understanding plant disease and pasture growth. They looked at perennial ryegrass, which has a fungus living inside it in a symbiotic relationship. "We focused on a particular gene in the fungus responsible for signal transduction. We knocked out that gene and reintroduced the modified fungus into the plant, and the results were dramatic," lead scientist Prof Barry Scott said. The plant's whole development was altered. "It was seriously stunted; it didn't grow very well. At the base of the grass there's usually a band of red pigments, but they were gone, and the fungus just grew out of control; the symbiosis had completely broken down," Professor Scott said.