biology poster

Hemileia vastatrix (Coffee Leaf Rust)

A fungus that is important to agriculture Christopher Chan

Abstract Hemileia vastatrix, commonly known as coffee leaf rust, is a parasitic fungus in the phylum Basidiomycota. It is important to agriculture because it causes premature defoliation in plants of genus Coffea, the source of coffee beans. Coffee leaf rust epidemics can be devastating for coffee farmers. Infected coffee leaves display yellow-orange lesions that look like rust. A complete fungal life cycle includes the processes of germination and sporulation. Specific temperatures and continual free water are requirements for germination. H. vastatrix spores, called urediniospores, penetrate the leaf’s stomata and grow into the plant tissue. Specialized hyphae absorb nutrients from the plant. Sporulation results in production of millions of new urediniospores. Coffee leaf rust is spread by both abiotic and biotic factors, including the wind, rain, animals, and insects. H. vastatrix displays an r-selected reproductive strategy and disseminates spores using the wind. Because the fungal life cycle depends on variable factors like temperature and presence of water, H. vastatrix must be able to weather hardships. Fungal ancestors that could produce many spore offspring and spread them over long distances using the wind may have been more successful at reproducing and passing their genetic material to future generations.

References

Phylogenetic Trees

Organismal Diversity Project BIOL 1302 General Biology 2

Department of Natural Sciences Spring 2013 – Dr. Griffard

Hemileia vastatrix

Evolutionary Adaptation Adaptation: Hemileia vastatrix uses the wind for mass spore dispersal.

•  Millions of urediniospores are produced during sporulation. The urediniospores are then released to the wind. •  Very little energy is invested into each individual offspring, a characteristic of r-selected species.

How did this adaptation arise?

•  Key: Fungal ancestors that had the ability to create numerous spores and harness wind dispersal may have been more successful at passing on their genetic material to future generations.

•  This adaptation may have arisen because of unpredictable or changing environmental conditions. •  Spore production depends on variable factors like elevation, temperature, and water levels. •  Reproductive success depends on the ability to thrive through unpredictable changes in climate and other factors.

Life Cycle The Hemileia vastatrix life cycle can be summarized by two steps:

1)  Urediniospore germination. a)  Requires free water and is optimal under temperatures

within the range of 18 to 25 C. b)  Urediniospores attach to stomata and develop germ tubes. c)  Specialized hyphae called haustoria penetrate the plant’s

tissue and draws nutrients. 2)  Sporulation.

a)  2 weeks after infection, new urediniospores form. This is usually the earliest that coffee leaf rust infection can be detected.

b)  Asexual reproduction forms new urediniospores. c)  A single lesion can release over 300,000 new

urediniospores with 5 months.

Ecology Hemileia vastatrix:

•  is an obligate parasite that cannot complete its life cycle without exploiting a suitable host. •  has a parasitic relationship with plants of genus Coffea. •  is a decomposer •  plays a key role in recycling carbon, nitrogen, and other elements •  requires certain environmental conditions, including and continual presence of free water •  can be found in every coffee producing region in the world except Hawaii.

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Steiman, Shawn. "Hemileia Vastatrix." Coffeeresearch.org. Coffee Research Institute, 12 Jan. 2006. Web. 08 Apr. 2013. Zivkovic, Bora. "BIO101 - Current Biological Diversity." Scientific American. Scientific American, 29 Oct. 2011. Web. 26 Feb. 2013.

Coffee plant infected by H. vastatrix.

Urediniospores emerge through stomata on coffee plant leaf.

Close-up view of coffee rust lesions.

Spread of coffee rust around the world.