Interactions of various Verticillium species in combination with V. albo-atrum on verticillium wilt disease development in potato

Verticillium wilt is an economically important disease that causes reduced tuber yields in potato. Pathogen population dynamics were studied during disease development following combined inoculations of potato with V. albo-atrum and various other Verticillium species. In greenhouse and field studies, three Verticillium species were examined: V. albo-atrum 'group 1', V. albo-atrum 'group 2' and V. tricorpus. Potato plants were inoculated with two out of the three species in various combinations of an aggressive (V. albo-atrum 'group 1') and weak (V. albo-atrum 'group 2' or V. tricorpus) pathogen. Initial inoculations occurred on the same date or with a weak species followed by an aggressive species four days later. Plant and soil samples were collected and relative population levels (RPLs) of each pathogen were determined using polymerase chain reaction (PCR) techniques. In combinations where pathogens were inoculated at the same time, RPLs of the weaker species did not exceed those of the aggressive species. In combinations where the weaker species were inoculated first, followed by the aggressive species four days later, the two weaker species were able to exceed RPLs and reduce visual wilt symptoms of V. albo-atrum 'group 1'. Implications of these findings on epidemiological aspects of these host-pathogen interactions are discussed. [PUBLICATION ABSTRACT]