A Comparison of the Endogenous Cytokinins in the Roots and Xylem Exudate of Nematode-resistant and Susceptible Tomato Cultivars

Abstract

Non-infested roots of a tomato cultivar (Roodeplaat Premier) susceptible to root-knot nema todes contained higher levels of endogenous cytokinins than non-infested roots of a nematode resistant cultivar (Master Fl). In both cultivars nematode infestation increased the cytokinin level in the roots. Sephadex LH-20 fractionation indicated that the xylem exudate of infested susceptible plants contained zeatin and zeatin riboside. In the roots of both cultivars a third compound, which co-eluted with zeatin glucoside, was present. The activity of all three cell division-inducing compounds was higher in the roots of susceptible plants than in roots of nematode-resistant plants. The present results support the hypothesis that cytokinins may be a controlling factor in the development of giant cells.