Comparative study of the fungicide Benomyl toxicity on some plant growth promoting bacteria and some fungi in pure cultures

Randa H. Elslahi 1 , Awad G. Osman 1 , Ashraf M. Sherif 1 , and Adil A. Elhussein 2
  • 1 Biofertilization Department, Environment and Natural Resource Research Institute, National Center for Research, Khartoum, Sudan
  • 2 Botany Department, Faculty of Science, University of Khartoum, Khartoum, Sudan


Six laboratory experiments were carried out to investigate the effect of the fungicide Benomyl on pure cultures of some plant growth promoting bacteria (PGPB) and some fungi. The highest LD50 was recorded for Bacillus circulans and proved to be the most resistant to the fungicide, followed by Azospirillum braziliense, while Penicillium sp. was the most affected microorganism. LD50 values for the affected microorganisms were in 21-240 orders of magnitude lower in comparison with the LD50 value for Azospirillum braziliense. The results indicate a strong selectivity for Benomyl against Rhizobium meliloti and Penicillium sp. when compared to other microorganisms tested. The highest safety coefficient was recorded for Bacillus circulans followed by Azospirillum braziliense, while Rhizobium meliloti, showed the lowest safety coefficient value compared to other bacteria. The lowest toxicity index was recorded for Bacillus circulans and Azospirillum braziliense. The slope of the curves for Bacillus sp. and Rhizobium meliloti was steeper than that of the other curves, suggesting that even a slight increase of the dose of the fungicide can cause a very strong negative effect. In conclusion, Benomyl could be applied without restriction when using inocula based on growth promoting bacteria such as symbiotic nitrogen fixers (Rhizobium meliloti), non-symbiotic nitrogen fixers (Azospirillum braziliense) or potassium solibilizers (Bacillus circulans), given that the fungicide is applied within the range of the recommended field dose.

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  • Cooksey DA. (1990). Genetics of bactericide resistance in plant pathogenic bacteria. Annu Rev Phytopathol 28: 201-219.

  • Daoud AS, Qasim NA, Al-Mallah NM. (1990). Comparison study on the effect of some plant extracts and pesticides on some phytopathogenic fungi. Mesopotamia Journal of Agriculture 22(4): 227-235.

  • Finney DJ. (1971). Probit Analysis (3rd edition). Cambridge University Press, Cambridge, UK.

  • Fravel DR, Deahl KL, Stommel JR. (2005). Compatibility of the biocontrol fungus Fusarium oxysporum strain CS-20 with selected fungicides. Biological Control 34: 165-169.

  • Gomez F, Salmeron V, Rodelas B, Mrtinez-Toledo MV, Gonzalez-Lopez J. (1998). Response of Azospirillum braziliense to the pesticides bromopylate and methidathion on chemically defined media and dialysed-soil media. Ecotoxicology 7(1): 43-47.

  • Kalinin VA, Bykov KV and Osman AG. (2002). Effects of Azoxystrobin on Soil Microorganisms under Laboratory Conditions. The British Crop Protection Council BCPC Conference - Pests & Diseases 4C-4: 279-284.

  • Kruglov UV. (1991). Soil Microflora and Pesticides. Agroprom, Moscow. [In Russian].

  • Odeyemi O, Alexander M. (1977). Use of fungicide-resistant rhizobia for legume inoculation. Soil Biol Biochem 9: 247-251.

  • Ogawa JM, Manji BT, Heaton CR, Petrie J, Sonoda RM. (1983). Methods for detecting and monitoring the resistance of plant pathogens to chemicals. In: Georghiou GP and Saito T. (Eds). Pest Resistance to Pesticides. Plenum Press, New York.

  • Omar SA, Abd-Alla MH. (1992). Effect of pesticides on growth, respiration and nitrogenase activity of Azotobacter and Azospirillum. World J Microbiol Biotechnol 8(3): 326-328.

  • Osman AG, Sherif AM, Elhussein AA. (2012). Sensitivity of some nitrogen fixers and the target pest Fusarium oxysporum to fungicide thiram. Interdiscip Toxicol 5(1): 25-29.

  • Paliwal A, Gurjar RK, Sharma HN. (2009). Analysis of liver enzymes in albino rat under stress of λ-cyhalothrin and nuvan toxicity. Biol Med 1(2): 70-73.

  • Revellin C, Giraud J-J, Silva N, Wadoux P, Catroux G. (2001). Effect of some granular insecticides currently used for the treatment of maize crops (Zea mays) on the survival of inoculated Azospirillum lipoferum. Pest Manag Sci 57(11): 1075-1080.

  • Shattock RC. (1988). Studies on the inheritance of resistance to metalaxyl in phytophthora infestans. Plant pathol 37: 4-11.

  • Srinivasulu M, Mohiddin GJ, Madakka M, Rangaswamy V. (2012). Effect of pesticides on the population of Azospirillum sp. and on ammonification rate in two soils planted to groundnut (Arachis hypogaea L.). Tropical Ecology 53(1): 93-104.

  • Sun YP. (1950). Toxicity index-an improved method of comparing the relative toxicity of insecticides. J Econ Entomol 43(1): 45-53. Lo CC. (2010). Effect of pesticides on soil microbial community. J Environ Sci Health B 45(5): 348-359.

  • Tepper EZ, Shilinkova UK, Perverzeva GE. (1993). Manual of microbiology, Mosco, kolas, 4th Edition. United States Environmental Protection Agency (US-EPA). (2005). Pesticide product database. Washington, DC.

  • ZinchenkoVA, Viatkina, NE, Afanaseva AU. (1974). Biological methods for determination the toxicity and residuals of pesticides. Methodological directions for laboratory and practical course “Chemical protection of plants”, Department of Chemical Plant Protection. Moscow Agricultural Academy.


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