Effect of temperature on Fusarium solani and F. tricinctum growth and disease development in soybean

Abstract

Fusarium solani and F. tricinctum are important root rot pathogens of soybean in the northern Great Plains of North America. The role of temperature on their growth was investigated in vitro at temperatures between 0 to 35ºC, while disease development in the soybean cultivar ‘Barnes’ was tested at 15°C, 20°C, 25°C and 30°C using several methods over 1 to 4 weeks. All experiments were conducted in a growth chamber. The effect of temperature on mycelial growth was modelled using an asymmetric logistic single peak model, which described fungal growth rate at temperatures of 8.5–34.3°C for F. solani and 3.1–32.2°C for F. tricinctum. The non-linear model estimated 29.3°C as the optimum temperature for growth of F. solani, and 24.4°C for F. tricinctum. Temperature had a significant effect on disease development in cotyledons and roots after 1-week incubation in rolled germination paper. The most favourable temperature for disease in cotyledons was 30°C for F. solani and 25°C for F. tricinctum. For roots, the optimal temperature for F. solani was also 30°C, but root disease by F. tricinctum was highest at 15°C. In infested soil after 4 weeks, lesion lengths on roots were longer and disease incidence was greater for F. solani at 30°C versus lower temperatures, whereas for F. tricinctum the optimum temperature for root disease was 15°C. The thermal specific characteristics of these pathogens implied disease development by F. solani is favoured by warmer temperatures, while in F. tricinctum it is favoured by cooler temperatures.