Soybean cultivars adapted to southern Brazil differ in their reaction to Globisporangium irregulare, G. ultimum var. sporangiiferum and Pythium conidiophorum

Abstract

AbstractIn Brazil there is little information on the reaction of soybean cultivars to Globisporangium and Pythium species that can cause damping‐off. Thus, the objective of this study was to characterize the reactions to Globisporangium irregulare isolate UPFOM03, G. ultimum var. sporangiiferum isolate UPFPAN06 and Pythium conidiophorum isolate UPFSA03 of 50 cultivars adapted to southern Brazil. The experiment was carried out twice in a randomized complete block design with three replications. A root rot assay was performed in a growth chamber and emergence (%), emergence speed index (ESI), total dry mass per seedling (TDM; g) and root rot severity index (RRSI) were determined. There was a significant (p < 0.05) difference among the cultivars on all the variables. The least susceptible cultivars to G. irregulare were BRS 5804, BMX Compacta, FPS 1867, BMX Fibra, BMX Apolo, M6410, M6210, BMX Elite and BRS 5601. However, the least susceptible cultivars to G. ultimum var. sporangiiferum were M6410, M6210, BMX Tornado, NS 6601, NS 5258, NS 6909, BMX Fibra, FPS 1954, M5917, BMX Delta, FPS 1867, BMX Cromo, NEO 610, BMX Elite, DM 61i59, BMX Apolo, BMX Compacta and M5947. Thirty‐six soybean cultivars were less susceptible to P. conidiophorum, which was also less aggressive than G. irregulare and G. ultimum var. sporangiiferum. In conclusion, there are some soybean cultivars that are less susceptible to the three oomycete isolates and should be preferred in fields with a history of damping‐off.