biotrophic

Biotrophic refers to organisms that obtain nutrients from living host tissue while keeping the host alive. The term is commonly used in plant pathology and mycology. Biotrophs are contrasted with necrotrophs, which kill host tissue and feed on the dead matter, and with hemibiotrophs, which begin life as biotrophs but later switch to necrotrophy.

In fungi and oomycetes, biotrophs often form specialized feeding structures such as haustoria that invaginate host cells or establish intimate intercellular interfaces to extract nutrients without immediately destroying the host. They tend to induce subtle symptoms and rely on living tissue to sustain growth. Many biotrophic pathogens are highly host-specific and can persist within their hosts for extended periods.

Examples of biotrophs include rust fungi (Puccinia spp.), powdery mildews (such as Erysiphe spp.), and downy mildews. Some biotrophs are obligate, meaning they cannot complete their life cycle without a living host, while others are facultative biotrophs, able to live on living tissue but also on dead matter under certain conditions. Because biotrophs avoid rapid host death, their management often focuses on strengthening host defenses, disrupting nutrient uptake, or preventing initial infection rather than relying on tissue necrosis.

Beyond pathogens, some endophytic organisms exhibit biotrophic lifestyles, living within plant tissues without causing disease and sometimes providing benefits to the host.