Rust of linseed and flax (autoecious rust) is caused by

Answer: Option D

Rust of linseed and flax (autoecious rust) is caused by Melampsora lini.
The pathogen is an obligate biotroph meaning that each stage of its cycle is dependent on having a living host. The direction between reproducing sexually or asexually is dependent on the availability of a host.
Sexually, the life cycle starts when basidiospores land on flax leaves and form pycnium during December and through January.