The Urochloa Foliar Blight and Collar Rot Pathogen Rhizoctonia solani AG-1 IA Emerged in South America Via a Host Shift from Rice.

The fungus Rhizoctonia solani anastomosis group (AG)-1 IA emerged in the early 1990s as an important pathogen causing foliar blight and collar rot on pastures of the genus Urochloa (signalgrass) in South America. We tested the hypothesis that this pathogen emerged following a host shift or jump as a result of geographical overlapping of host species. The genetic structure of host and regional populations of R.