Abstract
▪ Abstract Interest in the rust fungi derives from their success as plant pathogens. For example, the epidemic on coffee had serious economic and social impacts on diverse cultures. During the century, research on the rust germling shifted from a study of germling development, including a search for the signals that induce differentiation, to an examination of the genes expressed during host colonization. Research on host resistance was most influenced by Stakman, who studied the genetics and epidemiology of rust disease. His innovations enabled Flor to propose the gene-for-gene hypothesis, a concept that stimulated development of resistant crops, and led to research that gradually shifted during the century to an examination of the molecular basis of rust genetics.