Heteroecious

A heteroecious parasite is one that requires at least two hosts. The primary host is the host in which the parasite spends its adult life; the other is the secondary host. Both the primary host and an unrelated alternate host are required for the parasite to complete its life cycle. This can be contrasted with an autoecious parasite which can complete its life cycle on a single host species. Many rust fungi are prime examples of a heteroecious life cycle.^[1]

Parasitic heteroecious fungi include

• Gymnosporangium (Cedar-apple rust); the juniper is the primary (telial) host and the apple, pear or hawthorn is the secondary (aecial) host
• Cronartium ribicola (White pine blister rust); the primary host are white pines, and currants the secondary.
• Hemileia vastatrix (Coffee rust); Primary host is coffee plant; Unknown alternate host
• Puccinia graminis (Stem rust of wheat and Kentucky bluegrass); Primary hosts include: Kentucky bluegrass, barley, and wheat; Common barberry is the alternate host.
• Puccinia coronata (Crown Rust of Oats and Ryegrass); Oats are the primary host; Rhamnus spp. (Buckthorn) is alternate host.
• Phakopsora meibomiae and P. pachyrhizi (Soybean Rust); Primary host is soybean and various legumes. Unknown alternate host.

History

The phenomenon of heteroecy was first discovered by A.S. Ørsted in 1863.

• Ørsted, A.S. (1863) Om Sygdomme hos Planterne, som foraarsages af Snyltesvampe, navnlig om Rust og Brand og om Midlerne til deres Forebyggelse. Kjøbenhavn.

References

1. Schumann, G. & D'Arcy, C. (2010). Essential plant pathology. APS Press