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Population Structure of Cercospora kikuchii, the Causal Agent of Cercospora Leaf Blight and Purple Seed Stain in Soybean

July 2008 , Volume 98 , Number  7
Pages  823 - 829

G. Cai and R. W. Schneider

Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803.

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Accepted for publication 5 March 2008.

Random amplified polymorphic DNA (RAPD) and microsatellite-primed polymerase chain reaction (MP-PCR) were used to characterize 164 isolates of Cercospora kikuchii, most of which were collected from Louisiana. Plant tissue (seeds versus leaves), but not host cultivar, had a significant impact on pathogen population differentiation. Cluster analysis showed that the Louisiana population was dominated by a primary lineage (group I) with only a few Louisiana isolates belonging to the minor lineage that also included the non-Louisiana isolates (group II). A previous study showed that isolates could be differentiated according to vegetative compatibility groups (VCGs). However, RAPD and MP-PCR data demonstrated that isolates of C. kikuchii were not generally clustered according to these VCGs. Furthermore, genetic relationships within and between VCGs were examined using sequences of the intergenic spacer region of rDNA. These analyses showed that VCG is not an indicator of evolutionary lineage in this fungus. Our results suggest the likely existence of a cryptically functioning sexual stage in some portion of the C. kikuchii population.

© 2008 The American Phytopathological Society