Abstract
Phytophthora sojae is a major pathogen in cultivated soybeans world-wide. Although incorporating resistance genes has been an effective management tool for soybean breeders, surveys of soybean fields in the Midwest US indicate that some P. sojae strains are capable of overcoming all known resistance genes. While P. sojae is known to have a very narrow host range, it can also infect Lupinus (lupine), varieties of which may provide potential sources for novel resistance genes that can be genetically engineered into soybean. The chemotactic behavior of zoospores and pathogenicity of P. sojae strain P6497 towards 17 lupine lines were explored. The two soybean varieties Williams and Williams 82 that are susceptible and resistant against P. sojae P6497, respectively, were used as controls. Chemotaxis assays showed that there was no coherent pattern between the number of zoospores colonizing the root surface and plant tolerance or resistance to phytophthora root rot. Pathogenicity tests identified that two of the 17 lupine lines tested (LAB 18 and LL 35) were resistant to P. sojae infection. Phylogenetic analysis of these two resistant lupine lines with Old World lupines of the Mediterranean and North African regions, and New World lupines of America, indicated that they originated from the Old World.
Published Version
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