Soil suppressiveness against Macrophomina Phaseolina s.l. as affected by cyclic temperature regimes

Abstract

Effect of temperature on the survival of Macrophomina phaseolina s.l. (Mp) was tested under laboratory conditions using an incubation system programmed for a cyclic temperature regime, simulating soil solarization. Mp culture and soil with and without Mp were incubated under two cyclic temperature regimes, with maximum temperatures of 50 °C or 52 °C, simulating solarization processes, and at a constant temperature of 25 °C, as a control. Total fungal community and Mp levels were not affected negatively by constant temperature of 25 °C. However, total soil fungal community was significantly decreased at temperature regime of 50 °C, whereas Mp did not change significantly whether in soil mixture or as pure propagules culture. In Mp-amended soil treated by temperature regime of 50 °C, total fungal community decreased while Mp CFU number did not change significantly. However, temperature regime of 52 °C almost completely eradicated total fungal community, as well as that of Mp. When Mp was amended to soils after being treated at 50 °C and 52 °C temperature regimes and incubated for two additional weeks at 25 °C, an indirect temperature effects on Mp survival were apparent. The 50 °C pre-treatment did affect significantly neither the total fungal nor Mp levels. In soil previously treated by 52 °C, total fungal growth was somewhat decreased while Mp growth was promoted. The results suggest that Mp survival may be affected by temperature directly as well as indirectly via effects on total fungal population. Studying these biological factors may contribute to the control of Mp pathogen using environment-friendly methods.