The impact of temperature on the production and fitness of microsclerotia of the fungal bioherbicideMycoleptodiscus terrestris

Abstract

The impact of growth temperature was evaluated for the fungal plant pathogen Mycoleptodiscus terrestris over a range of temperatures (20Á368C). The effect of temperature on biomass accumulation, colony forming units (cfu), and microsclerotia production was determined. Culture temperatures of 24Á308C produced significantly higher biomass accumulations and 20Á248C resulted in a significantly higher cfu. The growth of M. terrestris was greatly reduced at temperatures above 308C and was absent at 368C. The highest microsclerotia concentrations were produced over a wide range of temperatures (20Á308C). These data suggest that a growth temperature of 248C would optimize the parameters evaluated in this study. In addition to growth parameters, we also evaluated the desiccation tolerance and storage stability of air-dried microsclerotial preparations from these cultures during storage at 48C. During 5 months storage, there was no significant difference in viability for air-dried microsclerotial preparations from cultures grown at 20Á308C (!72% hyphal germination) or in conidia production (sporogenic germination) for air-dried preparations from cultures grown at 20Á328C. When the effect of temperature on germination by air-dried microsclerotial preparations was evaluated, data showed that temperatures of 22Á308C were optimal for hyphal and sporogenic germination. Air-dried microsclerotial preparations did not germinate hyphally at 368C or sporogenically at 20, 32, 34, or 368C. These data show that temperature does impact the growth and germination of M. terrestris and suggest that water temperature may be a critical environmental consideration for the application of air-dried M. terrestris preparations for use in controlling hydrilla.

Statistical optimisation of process variables and large-scale production of Metarhizium rileyi (Ascomycetes: Hypocreales) microsclerotia in submerged fermentation

“…The three-dimensional response surfaces were plotted by using a statistically significant model to understand the interaction of the three important variables and determine the optimum level of each variable required for effective MS production. Although temperature had been shown to significantly influence MS production in other plant pathogenic fungi (Jackson et al 2011), it was an excluded variable in the RSM design to achieve optimum M. rileyi MS production because the optimised temperature range may not be suitable for M. rileyi growth. At 24-28°C, significantly higher biomass accumulation and MS production were observed, whereas at temperatures above/below this range, the growth of M. rileyi was greatly reduced (data not shown).…”