Melampsora lini is a species of fungus and plant pathogen found in Ireland and commonly known as flax rust.

[1] The pathogen is an obligate biotroph meaning that each stage of its cycle is dependent on having a living host.

Sexually, the life cycle starts when basidiospores land on flax leaves and form pycnium during December and through January.

[4] The pathogen prefers an environment in the temperate plains or hills of the United Kingdom rather than in high altitude and cold conditions.

These proteins help provide resistance against fungi, oomycetes, bacteria, viruses, nematodes, insects, and parasitic plants.