Genetic Variation for Pathogen Resistance in Tall Morningglory. Ellen L. Simms, Department of Ecology and Evolution, University of Chicago, 1101 E. 57th Street, Chicago, IL 60637. . Plant Dis. 77:901-904. Accepted for publication 20 April 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0901.

An experimental population of tall morningglory (Ipomoea purpurea) was established from the progeny of a replicated diallel design to assess the extent of heritable genetic variation in damage by the naturally occurring fungal pathogens Colletotrichum dematium and Coleosporium ipomoeae. Resistance to both pathogens varied significantly among paternal half-sib families, indicating significant levels of heritable variation in these traits. In addition, resistance to Coleosporium ipomoeae appears to be controlled at least in part by a major gene with a dominant resistance allele. These results suggest that increased resistance to Coleosporium ipomoeae and C. dematium would evolve if either was used as a mycoherbicide to control tall morningglory. The importance of these results to the durability of mycoherbicides is discussed.