INTERFERENCE BY NON-HOST PLANT ROOTS AND ROOT EXUDATES IN THE INFECTION PROCESSES OF <I>PHYTOPHTHORA NICOTIANAE</I>

Abstract

<List><ListItem><ItemContent> • The roots of non-host plant interfere infection of <i>Phytophthora nicotianae.</i> </ItemContent></ListItem><ListItem><ItemContent> • Vanillin and other compounds play key roles in antimicrobial activity of fennel roots. </ItemContent></ListItem><ListItem><ItemContent> • ROS accumulation is the potentially mechanism involved in inhibition of antimicrobial compounds on <i>P. nicotianae</i>. </ItemContent></ListItem></List> Crop rotations are widely used because they can significantly reduce the incidence of pests and diseases. The interactions between non-host roots and pathogens may be key in the inhibition of soilborne pathogens in crop rotations. Interactions between fennel (<i>Foeniculum vulgare</i>) roots/root exudates and <i>Phytophthora nicotianae</i> were investigated because of the known allelopathy between fennel and tobacco (<i>Nicotiana tabacum</i>). The effects of the key compounds in the fennel rhizosphere on the mycelial growth and zoospore behavior of <i>P. nicotianae</i> were assessed. The roots of fennel attracted <i>P. nicotianae</i> zoospores and inhibited their motility and the germination of cystospores, with some cystospores rupturing. 4-ethylacetophenone, vanillin and N-formylpiperidine were consistently identified in the fennel rhizosphere and were found to interfere with the infection of <i>P. nicotianae</i>, especially vanillin. Hyphae treated with these compounds produced more abnormal branches and accumulated reactive oxygen species. These interspecific interactions between non-host roots and pathogens were found to be an important factor in the inhibition by fennel of infection by <i>P. nicotianae</i>.