Characterization of Phytophthora resistance in soybean cultivars/lines bred in Henan province

Deployment of resistant soybean cultivars is the most effective and economical method of controlling Phytophthora root rot (PRR) incited by Phytophthora sojae, and characterization of Phytophthora resistance of the soybean cultivars greatly facilitates the effective utilization. The objective of this study was to characterize the resistance phenotype in 30 soybean cultivars/lines bred in Henan province and 4 ancestral cultivars which were inoculated with 26 P. sojae pathotypes. The 34 soybean cultivars/lines showed 34 different reaction types of resistance to 26 P. sojae pathotypes. The reaction types produced on the cultivars/lines were compared with those produced on the differential lines to postulate which Rps gene was present. The gene Rps5 and Rps3a or gene combination Rps3a+5 were postulated to be present in Zhoudou17 and Zheng77249, respectively. The other 32 cultivars/lines exhibited novel reaction types that were different from known single or two Rps gene combinations. The cluster analysis of the reaction types revealed 10 groups among the 34 soybean cultivars/lines, 17 differentials and the cultivar Williams at the similarity coefficient 0.6540. This study indicated that Phytophthora resistance was extremely diverse in this region. The cultivars/lines with broad spectrum resistance could provide effective sources of resistance for the control of PRR in the future.