Comparison of Baiting Techniques for Recovering Phytophthora sojae from Soybean Fields in Iowa

Abstract

Understanding the diversity of a pathogen is important for developing disease management recommendations. In the Phytophthora root and stem rot–soybean pathosystem, P. sojae is characterized into pathotypes based on the ability of the pathogen to cause disease on soybean genotypes that each contain a different resistance Rps gene. To understand the diversity of P. sojae in an area, isolates of the pathogen may be recovered by baiting soil samples. In this research, we compared two commonly used methods for baiting P. sojae: the leaf disc method and the seedling method. More isolates of P. sojae were recovered using the leaf disc baiting method (P < 0.01), and more pathotypes were detected within this population (P < 0.01). Mean complexity of the two populations and the simple, Gleason, and Shannon diversity indices also differed (P < 0.01). However, the percent of isolates that caused disease on each Rps gene did not differ between methods. Thus, either method could be used to characterize pathotypes of P. sojae present in an area to provide data to soybean breeders and agronomists for deployment of Rps genes in soybean cultivars.