Abstract
To investigate the action mechanism of sulfonate anionic surfactant against plant viral infection, inhibitory action of sodium and calcium salts of branched dodecylbenzenesulfonic acid (abbreviated as DBS-Na for the former, DBS-Ca for the latter and DBS for both) to tabacco mosaic virus (TMV) ordinary strain was studied using the French bean local lesion assay method. DBS-Ca inhibited the local lesion formation by 90% or more at 1, 000ppm when added in TMV inoculum, at 2, 000ppm when applied after TMV inoculation and at 2, 500ppm when applied prior to inoculation of TMV. The inhibitory effect of DBS-Na was somewhat less than that of DBS-Ca. When DBS-Ca was added in TMV inoculum, the inhibition of local lesion formation was primarily dependent upon the concentration of DBS-Ca itself, and little upon the concentration proportion of DBS-Ca to TMV or the incubation period in which they were mixed. DBS-Ca at 2, 000ppm, when applied within ca. 4hr after TMV inoculation, almost completely inhibited local lesion formation. Experiments by ultracentrifugation, Schlieren pattern measurement and gel filtration indicated that disintegration of TMV by DBS or absorption or reaction between them was little involved in the inhibitory effect. Also, the inhibitory effect of DBS-Ca incorporated through the petiol of French bean from aqueous solution was estimated, and the inhibition was remarkable at 200ppm or more of DBS-Ca in the solution. The results described above suggest that the inhibitory action of DBS to TMV infection is not due to the disintegration or inactivation of TMV but due to the depression of viral replication resulting from the disturbance in metabolism of host cell and in the function of the membrane at an early stage of TMV infec tion in that cell.
