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Effect of Carbon Disulfide (CS2) Emission by Acacia tortilis subsp. raddiana

By walaa on September 23,2008


Mohamed S. Zaghloul, Raafat H. Abd El-Wahab, and Samira R. Mansour 


       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 percent 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 the chemical and physical characterization of the growing soil. 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.

Key words: Carbon disulfide, Acacia tortilis subsp. raddiana, rhizosphere, biocontrol.

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