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Coffee Rust

Scientific Name
Hemileia vastatrix
Scientific Author
Berk. & Broome
Taxonomy
(Urediniomycetes, Uredinales)
Status
Exotic species - absent from Australia
Reliability
High
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Diagnostic Images (27)
Diagnostic Notes

Symptoms

Yellowish-orange, powdery, rounded blotches occur on the underside of leaves, which correspond to a chlorosis of the upper surface. Later, the centre of the old pustules becomes necrotic. Premature defoliation and die-back of the branches can occur.

 

The fungus

Spermogonia and aecia unknown. Sori hypophyllous, densely scattered and giving a powdery appearance on yellowish-orange rounded blotches about 3-25 mm in diam., consisting of numerous narrow interwoven ‘feeder” hyphae and ± rounded cells below the stomata, bearing clavate filaments emerging through the stomata, whose tips bear numerous pedicels on which the spores are borne. Urediospores ± reniform, 28-36 x 18-28 µm, wall hyaline, strongly warted on the convex face, smooth on the straight or concave face, 1 µm thick (Laundon & Waterston 1964b). Teliospores are rarely found. Telia as the uredinia, hypophyllous; teliospores often produced in uredinia, sometimes in teliosori, borne in cluster on short pedicels, 1-celled, spherical or napiform and smooth with aterminal papilla, 16-25 × 19-22 µm, borne. Teliospores germinate in situ by producing a promycelium, from which four spherical basidiospores are formed (Coutinho et al. 1995).

 

Fungal infection

 

The initiation of the dycariotic phase of H. vastatrix on coffee leaves involves specific events including appressorium formation over stomata, penetration inter- and intracellular colonization (Rijo & Rodrigues Jr. 1977, Tiburzy et al. 1983, Coutinho et al. 1993, Martins & Moraes 1996, Silva et al. 1999, 2002). Thus, in susceptible coffee leaves, after urediospore germination and appressorium differentiation over stomata the fungus penetrates forming a penetration hypha that grew into the substomatal chamber. This hypha produces at the advancing tip two thick lateral branches; each hypha and its branches resembled in the whole an anchor. From each lateral branch of the anchor is borne a hypha (haustorial mother cell – HMC), the subsidiary cells being the first invaded by haustoria (which formation started around 36h post-inoculation). The fungus pursued its growth giving rise to sporulation around 20 days post-inoculation (Rijo & Rodrigues 1977, Silva et al. 1999, 2002).

 

 

Note: H. vastatrix differs from H. coffeicola, which also occurs on Coffea spp., by having yellow-orange coloured spots on the leaf rather than being scattered over the entire leaf surface; and by urediniospores which have smaller and more numerous spines (Laundon & Waterston 1964a,b).
More Information
Specimen Contact
Dr Jose Liberato
Author
Liberato JR & Silva MC
Created
20/12/2005 04:37 AEST
Last Updated
01/10/2006 12:42 AEST
Citation
Liberato JR & Silva MC (2005) Coffee Rust (Hemileia vastatrix) Updated on 10/1/2006 12:42:23 PM Available online: PaDIL - http://www.padil.gov.au.
Image Use
Free for use under the Creative Commons Attribution 3.0 Australia License

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