Which one of the following rusts is autoecious in nature?

Correct option is A

· Correct answer: (a) Melampsora lini
· Melampsora lini is autoecious, meaning it completes its entire life cycle on a single host plant. This type of rust does not require a secondary host plant.
Other options:
· (b) Puccinia graminis: This is a heteroecious rust, requiring two different host plants for its life cycle.
· (c) Puccinia coronata: Also heteroecious, requiring two different hosts.
· (d) Phakopsora meibomiae: A heteroecious rust as well, needing two hosts.