Gymnosporangium is a genus of heteroecious plant-pathogenic fungi which alternately infect members of the family Cupressaceae, primarily species in the genus Juniperus (junipers), and members of the family Rosaceae in the subfamily Amygdaloideae (apples, pears, quinces, shadbush, hawthorns, rowans and their relatives). The common name cedar-apple rusts has been used for these fungi. According to the Dictionary of the Fungi (10th edition, 2008), there were 57 species in the genus. The basidiospores are released and travel on the wind until they infect an apple, pear, hawthorn or suitable tree.
On the secondary hosts, the fungus produces yellowish depressions on the leaves. It also infects the fruit, which grows whitish tubes like a Medusa head. These are the spore tubes. These aeciospores must then infect a juniper to complete the life cycle. All the types of spores can spread over long distances.
Due to the economic impacts of the rusts in some areas where orchards are of commercial importance, some regions have attempted to ban the planting of and/or eradicate the coniferous hosts.
In 2020, the monotypic family Gymnosporangiaceae was proposed to accommodate Gymnosporangium. As accepted by Wijayawardene et al. 2020.
Selected species and hosts
{| class="wikitable"
!align="left"|Species
!align="left"|Primary host
!colspan=1|Secondary host
!colspan=1|Common name
|-
|Gymnosporangium amelanchieris
| Juniperus sect. Juniperus
| Amelanchier
|-
|Gymnosporangium clavariiforme
| Juniperus sect. Juniperus
| Amelanchier, Crataegus, Pyrus
| Tongues of Fire
|-
|Gymnosporangium clavipes
| Juniperus
| Crataegus, Cydonia
| Cedar-quince rust, quince rust
|-
|Gymnosporangium cupressi
| Cupressus
| Amelanchier
|-
|Gymnosporangium dobroznakovii
| Juniperus sect. Juniperus
| Pyrus
|-
|Gymnosporangium fusisporum
| Juniperus sect. Sabina
| Cotoneaster
|-
|Gymnosporangium gaeumannii
| Juniperus communis
| (not known)
|-
|Gymnosporangium globosum
| Juniperus
| Crataegus
| Cedar-hawthorn rust, American hawthorn rust
|-
|Gymnosporangium libocedri (Now Gymnotelium blasdaleanum, Pucciniaceae family)
| Calocedrus
| Amelanchier
| Pacific Coast pear rust,
|}
Full list of species
As accepted by Species Fungorum;
Other sources
- Phillips, D.H., & Burdekin, D.A. (1992). Diseases of Forest and Ornamental Trees. Macmillan.
- Scharpf, R.F., ed. (1993). Diseases of Pacific Coast Conifers. USDA Forest Service Agricultural Handbook 521.
External links
- Forestry Images: Gymnosporangium
- Photo of Gymnosporangium sabinae on Juniperus sabina