A survey of soybean germplasm for resistance to Phytophthora sojae

Phytophthora root and stem rot of soybean caused by Phytophthora sojae is a destructive disease affecting soybean production regions throughout the world. The utilization of resistant cultivars is the most economical and environmentally safe method for controlling this disease. This work aims to screen the effective sources of special and partial resistance for the development of resistant cultivars. A total of 611 soybean germplasm lines from three ecological regions were evaluated for their responses to three P. sojae strains, namely, PNJ1, PNJ3, and PNJ4, using the hypocotyl inoculation technique. The soybean germplasm lines elicited eight different reaction types with three strains. Among these, 106 were resistant and 253 were susceptible to the three strains. A total of 123 soybean germplasm lines identified as susceptible to the three strains by the hypocotyl inoculation method were evaluated for partial resistance to PNJ1 using the slant board assay. Thirty-nine cultivars displayed high levels of partial resistance to PNJ1. The results of this study can be utilized to plant appropriately resistant cultivars in infected fields and to provide good breeding materials.