What is a key characteristic of the life cycle of Plasmodiophora brassicae?

A key characteristic of the life cycle of Plasmodiophora brassicae, the causal agent of clubroot disease in cruciferous crops, is its ability to remain dormant in the soil. This pathogen produces resting spores that can survive in the soil for several years, allowing it to persist even in the absence of host plants. This dormancy is crucial for its survival and ability to infect new host plants when conditions become favorable, highlighting the importance of soil management in controlling its spread.

The other options refer to different mechanisms associated with plant pathogens. Insect vectors are crucial for certain pathogens, but Plasmodiophora brassicae does not require them for transmission. Transmission via seed is another pathway utilized by many pathogens, but this specific pathogen does not use seeds as a primary means of spreading. Similarly, while some pathogens can infect plants through foliar contact, Plasmodiophora brassicae specifically infects the roots of the host plants, not through foliar means. Therefore, the dormancy in the soil is indeed a defining characteristic of its life cycle.