In Vitro Study of Toxicity of Soluble Sulphides To Three Nematodes Parasitic On Rice in Senegal

Abstract

Toxicity of sulphides to three species of nematodes parasitic on rice from Senegal (Hirsch" n i e h oryzaë, H. spinicandata and Tyleizchorhyizckvs irnashhoodi) was studied in vitro using three different methods.A Sulphide Time Unit (STU) was defined related to the average concentrations of sulphides and their variations during the tests.With hydrogen sulphide dissolved in water, the very low p H increased nematode mortality. When hydrogen sulphide was dissolved in a buffered medium used for bacterial culture, mortality was lower but a shock effect appeared due to sudden contact with high concentrations of sulphides and toxicity of some of the components of the medium. When hydrogen sulphide was produced by sulphate reducing bacteria a similar shock effect was still observed, but only when high concentrations were reached within 1 or 2 days: in such experiments nematodes were killed by low STU, and differences were observed in resistance of the three species. However, when sulphide accumulated more slowly, i.e., when lethal concentrations were reached in 3 or more days, the sensitivity of the three species was similar: 50% mortality was obtained at about 120-130 STU.The possibility of using sulphate reducing bacteria for biological control of parasitic nematodes of rice is discussed.

Exoenzymes and metabolites related to the nematicidal effect of rhizobacteria on Xiphinema index Thorne & Allen

“…Another volatile metabolite with reported nematicidal action is hydrogen sulphide (Rodriguez‐Kabana et al . ; Jacq and Fortuner ); however, there are no recent investigations related to its production in rhizobacteria or its effect on X. index . H 2 S is liberated into the media by the B. megaterium FB133M, B. thuringiensis FS213P and B. amyloliquefaciens FR203A strains; nevertheless, further research has to be developed to demonstrate the direct effect on nematodes because it is probable that the filtrate does not contain it, as it is a volatile element.…”

Pest categorisation of Hirschmanniella spp.

“…have been reported to reduce Hirschmanniella spp. Populations (Jacq and Fortuner, ). Chemical control: Use of nematicides can significantly reduce the population of Hirschmanniella spp. and increase yields of rice (Prot, ).…”