Transmission of Tobacco Necrosis Virus to Tobacco Callus Tissues by Zoospores of Olpidium brassicae

Abstract

MOREL1 infected cultures of plant callus tissue with some, but not all, of the obligate parasites he tested. Thus, with fungi, he succeeded with Plasmopara viticola and Uncinula necator, but not with several species of rust fungi on callus from susceptible host plants. He also infected tobacco callus with tobacco mosaic virus, but this is difficult and most work with plant viruses in tissue cultures has consequently been done with tissues taken from plants already systemically infected. Unwounded callus tissues are immune from infection by viruses, and although tissues can be infected by pricking with fine needles dipped in concentrated inoculum, the method is not always successful2. We have now found that tobacco callus tissue can be readily infected with tobacco necrosis virus with the aid of Olpidium brassicae, an obligately parasitic fungus that was known previously only to infect plant roots. Teakle3,4 showed that Olpidium aids the infection of roots by this virus, and we have confirmed this.