Effect of AL-toxin Produced by Alternaria alternata Tomato Pathotype on Cultured Roots of Tomato.

Abstract

The effect of AL-toxin produced by Alternaria alternata tomato pathotype on susceptible and resistant plants was investigated by employing a quantitative, simple and easy assay system using cultured roots of tomato. Root growth and root cell viability were examined by weighing and MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-Biphenyl tetrazolium bromide] colorimetric assay, respectively. Cultured roots of susceptible cv. Mie First incubated in culture media containing different concentrations of AL-toxin I showed a detectable reduction and complete inhibition of the growth at toxin concentrations of 0.01 and 1μg/ml, respectively. The growth of cultured roots of resistant tomato cv. Saturn was significantly and completely reduced at toxin concentrations of 0.1 and 10μg/ml, respectively. When the root viability was determined by the colorimetric assay using MTT, the viability of susceptible cultivar was significantly reduced at a toxin concentration of 1μg/ml, two days after treatment, while reduction in the viability of resistant cultivar was not detected even at a toxin concentration of 10μg/ml. These results indicate that the use of cultured roots of tomato may contribute to a quantitative and qualitative determination for evaluating the host specific mode of action of AL-toxin.