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Growth rate and trapping efficacy of nematode-trapping fungi under constant and fluctuating temperatures
A S Fernández1, M Larsen, J Wolstrup
1Danish Centre for Experimental Parasitology, Department of Veterinary Microbiology, Royal Veterinary and Agricultural University, Frederiksberg C. asf@kvl.dk
Abstract:
The effect of temperature on radial growth and predatory activity of different isolates of nematode-trapping fungi was assessed. Four isolates of Duddingtonia flagrans and one isolate of Arthrobotrys oligospora were inoculated on petri dishes containing either cornmeal agar (CMA) or faecal agar and then incubated for 14 days under three different constant and fluctuating temperature regimes. The radial growth was similar on the two substrates at each temperature regime. All fungal isolates showed a higher growth rate at a constant 20 degrees C. At 10 degrees and 15 degrees C, all D. flagrans isolates showed very similar patterns of radial growth at both constant and fluctuating temperatures. At 20 degrees C, they grew significantly faster at constant than at fluctuating temperatures. A. oligospora grew significantly faster than all D. flagrans isolates except when incubated at a fluctuating 20 degrees C. Spores of each fungal isolate were added to faecal cultures containing eggs of Cooperia oncophora at a concentration of 6250 spores/g faeces. The cultures were incubated for 14 days at the same temperature regimes described above. Control faeces (without fungal material) were also cultured. More larvae were recovered from the fungus-treated cultures incubated at a constant 10 degrees or 15 degrees C than from those incubated at the respective fluctuating temperatures, except for one D. flagrans isolate. Incubation at 20 degrees C showed the opposite effect. The general reduction observed in the number of nematode larvae due to fungal trapping was 18-25% and 48-80% for a constant and fluctuating 10 degrees C, 70-96% and 93-95% for a constant and fluctuating 15 degrees C, and 63-98% and 0-25% for a constant and fluctuating 20 degrees C, respectively.
Insights
Nematode-trapping fungi, Duddingtonia flagrans and Arthrobotrys oligospora, show varied growth and predatory activity based on temperature. Constant temperatures, especially 15 and 20°C, generally enhance fungal efficacy in reducing nematode larvae.
Area of Science:
- Mycology
- Nematology
- Environmental Microbiology
Background:
- Nematode-trapping fungi (NTF) are crucial biological control agents against parasitic nematodes.
- Temperature significantly influences fungal growth and predatory efficiency, impacting their efficacy in different environments.
Purpose of the Study:
- To investigate the effects of constant and fluctuating temperature regimes on the radial growth and predatory activity of Duddingtonia flagrans and Arthrobotrys oligospora isolates.
- To determine optimal temperature conditions for NTF to control nematode populations.
Main Methods:
- Four isolates of D. flagrans and one of A. oligospora were cultured on cornmeal agar and faecal agar under three temperature regimes (10, 15, 20°C) with constant and fluctuating conditions.
- Radial growth was measured after 14 days.
- Predatory activity was assessed by incubating fungal spores with Cooperia oncophora eggs in faeces for 14 days at the same temperature regimes, followed by nematode larval counts.
Main Results:
- Radial growth was optimal at a constant 20°C for all isolates. D. flagrans showed similar growth at 10 and 15°C under constant and fluctuating temperatures.
- A. oligospora exhibited faster growth than D. flagrans, except at fluctuating 20°C.
- Nematode larval reduction was higher under constant temperatures (10°C and 15°C) compared to fluctuating ones, with significant reductions (70-96% at 15°C). However, at 20°C, fluctuating temperatures resulted in higher larval reduction (0-25%) than constant temperatures (63-98%).
Conclusions:
- Temperature regimes critically affect the growth and nematode-trapping efficacy of D. flagrans and A. oligospora.
- Constant temperatures, particularly 15°C, are generally more favorable for NTF activity in reducing nematode larvae.
- The optimal temperature strategy for NTF efficacy varies, with fluctuating conditions at 20°C showing potential for specific isolates.
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