Tumor Formation by Attenuated Crown-Gall Bacteria in the Presence of Growth-Promoting Substances

Abstract

An attenuated culture of Phytomonas [Agrobac-terium]. tumefaciens (A66), itself incapable of producing tumors, will do so in tomato stems (var. Bonny Best) when supplemented by growth-promoting substances. a-naph-thalene acetic acid, [gamma]-indole butyric acid and [beta]-indole acetic acid, also incapable of tumor production alone, will do so when combined with these attenuated bacteria. The first yields tumors most closely resembling those produced by virulent P. tumejaciens. Tumors produced by this double treatment are sometimes bacteria-free, but when not, the recovered bacteria are still nonvirulent. The altered host cells are capable of transplantation in series and retain their tumor-inducing capacity, perhaps indefinitely. The difference between the virulent and the attenuated bacteria may lie in the amt. of growth substances produced either by the bacteria or by the host under their influence.