Question

Fungi that requires two different hosts to complete its life cycle is called
A. Homothallic
B. Heterothallic
C. Heteroecious
D. Autoecious

Answer 1

Hint: All rusts are forced parasites, which means that they need a living host to complete their life cycle. They usually do not kill the host plant, but they can significantly reduce growth and yield.

Complete Answer:
- A heteroecious parasite is one that needs at least two hosts. The main host is the host where the parasite spends its adult life; the second host is the secondary host. In order for the parasite to complete its life cycle, both the primary host and the unrelated alternate host are required.
- This can be contrasted with an autoecious parasite that can complete its life cycle on a single host species. A number of rust fungi have heteroecious life cycles.
- In heterothallic fungi, two separate individuals contribute nuclei to the development of a zygote.
- Homothallic refers to the possession, within a single organism, of resources for sexual reproduction, i.e. possessing male and female reproductive structures on the same thallus. The opposite sexual role is performed by different cells of a single mycelium.
- There are definite patterns of relationships with host plant groups and the rust fungi that parasitize them.

Thus the correct answer is option(C) Heteroecious.

Note: Some of the rust fungi, particularly Puccinia and Uromyces, are species capable of parasitizing the plants of many families. Certain rust genera tend to be confined to some classes of plants. Host restriction can extend in heteroecious species to both phases of life cycle or to only one phase of life cycle.