H. S. McNabb
First and fifth authors: Departments of Forestry and Plant Pathology, Iowa State University, Ames 50011; second author: USDA Forest Service, Southern Research Station, Southern Institute of Forest Genetics, 23332 Highway 67, Saucier, MS 39574; third author: USDA Forest Service, Rocky Mountain Research Station, Forestry Sciences Laboratory, 1221 South Main, Moscow, ID 83843; and fourth author: Department of Forestry, Iowa State University, Ames 50011
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Accepted for publication 26 May 2000.
In the north central United States, leaf rust caused by Melampsora medusae is a major disease problem on Populus deltoides. In this study we identified molecular markers linked to a M. medusae resistance locus (Lrd1) that was segregating 1:1 within an intraspecific P. deltoides family (C9425DD). Previous field results were confirmed in the controlled environment of a growth chamber through an excised whole-leaf inoculation method. Using bulked segregant analysis we identified two random amplified polymorphic DNA (RAPD) markers (OPG10340 and OPZ191800) that are linked to Lrd1. Based on segregation in a total of 116 progeny, the genetic distances between OPG10340 and OPZ191800 and the resistance locus were estimated as 2.6 and 7.4 Haldane centimorgans (cM), respectively. Multipoint linkage analyses strongly suggest the most likely order for these loci is Lrd1, OPG10340, and OPZ191800. These markers may prove to be instrumental in the eventual cloning of Lrd1, as well as for marker-assisted selection of leaf-rust resistant genotypes.
polymerase chain reaction,
The American Phytopathological Society, 2000