Effect of Carbon Disulfide (CS2) Emission by Acacia tortilis subsp. raddiana on Microbial Population in the Rhizoshpere

Document Type : Original Article

Authors

1 Botany Department, Faculty of Science, Suez Canal University, Ismailia, Egypt

2 Botany Department, Faculty of Science, Suez Canal University, 41522 Ismailia, Egypt

Abstract

Roots of Acacia tortilis subsp. raddiana seedlings were proved to emit carbon disulfide (CS2); a low
molecular weight, volatile, highly flammable, sulfur-containing molecule with bacteriostatic, fungicidal,
nematicidal and insecticidal properties that has inhibition influence on microbial communities in the
rhizosphere of A. tortilis seedlings. Total count of bacterial cells, colony forming unites (CFU) of
actinomycetes and population of nitrifying bacteria around roots of A. tortilis seedlings grown on
different soil types, were dramatically inhibited compared to the control. Inhibition by CS2 was
represented by reduction percentage of bacterial count which reached its maximum value (99.8%) by the
end of the experiment (eight weeks after transplanting seedlings) on sandy-loam soil. However, with
nitrifying bacteria highly significant inhibition was recorded at six weeks with 96.1%. Loamy-sand soil
significantly recorded less reduction percentage of nitrifying bacteria that reached the peak by the end of
six week with 80.0%. Inhibition of CFU of actinomycetes was significantly less in compare to other
organisms in different tested soils. Sandy soil was less affected by CS2 emission and showed temporary
growth inhibition. Growth recovery of actinomycetes was observed after six weeks of transplanting.
Growth of A. tortilis significantly varied with soil type and showed the best growth in loamy-sand soil.
Sandy soil showed promising growth rate even it was significantly less than other soil types. The
obtained results suggest that CS2 production is regulated by plant growth which is in turn affected by soil
chemical and physical characteristics. The study recommends that Acacia tortilis subsp. raddian plants
may have an agronomic use in crop rotations or intercropping because root-produced CS2 may act as a
deterrent to soil pathogens.

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