Which characteristics are typical of necrotrophic pathogens like those causing apple scab?

Necrotrophic pathogens, such as those that cause apple scab, are distinguished by their ability to kill host tissues to obtain nutrients. This mechanism allows them to thrive on the breakdown of dead plant material, which provides them with the necessary resources for reproduction and spread.

These pathogens typically invade plant tissues and release enzymes or toxins that facilitate the destruction of the host cells. Once the plant tissue is killed, the necrotrophic pathogens can effectively colonize and utilize the dead plant material for nourishment. This strategy contrasts with biotrophic pathogens, which require living tissues and often live in a more symbiotic manner with their hosts, deriving nutrients without killing them immediately.

In the context of the other choices:

• Those that require living tissue for survival are indicative of biotrophic pathogens, not necrotrophic ones.

• The decomposition of dead organic material is a function of certain saprophytic organisms, which is not the primary focus of necrotrophic pathogens.

• Forming symbiotic relationships with hosts is characteristic of mutualistic or biotrophic organisms, which also does not apply to necrotrophic pathogens that typically rely on killing host tissues for their nutrient source.

Understanding these distinctions is crucial for effective management and control strategies in agriculture and horticulture,