biotroph

Biotrophs are organisms that obtain nutrients from living host tissue, keeping the host alive while feeding. In plant pathology, biotrophs colonize living plant cells and rely on the host’s metabolism, rather than killing tissue outright to feed. They contrast with necrotrophs, which kill cells and feed on the resulting debris, and with hemibiotrophs, which start as biotrophs but later switch to necrotrophy.

Feeding structures and lifestyle are characteristic of many biotrophic plant pathogens. They often form haustoria, specialized structures that invaginate the host cell membrane to extract sugars and nutrients while maintaining host cell viability. Biotrophs typically have narrow host ranges and intricate life cycles, sometimes involving alternate hosts or multiple spore stages. Symptoms can include chlorosis, mosaics, powdery growth, or rust pustules, often without rapid tissue death.

Common biotrophic groups include rust fungi (Pucciniales) and powdery mildews (Erysiphales), as well as downy mildews. Some oomycetes, such as Albugo candida, are also biotrophic. Because living tissue is required, many biotrophs are difficult to culture in artificial media and depend on host-derived nutrients for growth and reproduction.

Management of biotrophic diseases emphasizes preventing infection and spread. Strategies include using resistant cultivars, eliminating alternate hosts, rigorous sanitation to remove inoculum, and timely fungicide applications that target spore germination or haustorial formation. Ongoing research into host–pathogen interactions and effector proteins informs efforts to achieve durable resistance.