Glomus macrocarpum
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| Glomus macrocarpum | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Glomeromycota |
| Class: | Glomeromycetes |
| Order: | Glomerales |
| Family: | Glomeraceae |
| Genus: | Glomus |
| Species: | G. macrocarpum |
| Binomial name | |
| Glomus macrocarpum Tul. & Tul. 1845 | |
Glomus macrocarpum is a vesicular-arbuscular endomycorrhizal plant pathogen in the Glomeraceae family of fungi. Also occasionally known as Endogone macrocarpa, G. macrocarpum is pathogenic to multiple plants, including tobacco and chili plants. G. macrocarpum was first discovered in the French woodlands by the Tulasne brothers in the early to mid 1800s.[1] Their first known description of G. macrocarpum was published in the New Italian Botanical Journal in 1845.[1] G. macrocarpum has since been documented in over 26 countries, including Australia, China, and Japan for example. G. macrocarpum is frequently found in grassy meadows, forests, greenhouses, and fruit orchards. It is known for its small, round-edged, and light brown to yellow-brown sporocarp. G. macrocarpum is sometimes known as the Glomerales truffle.[1]
Morphology
The sporocarp of G. macrocarpum is small, usually measuring up to about 12 millimeters in diameter. The sporocarp shape ranges from globose, subglobose, elongate, to irregular. The sporocarp is also often observed to have soil (primary substrate) embedded in its surface. When the peridium is present, it appears white with a cottony texture.[2] The sporocarp color ranges from yellow-brown to light brown.
Chlamydospores that act as resting spores or survival structures are present. These allow the fungus to remain dormant during inadequate germination conditions. Once appropriate germination conditions are reached, chlamydospores form germ tubes to germinate into hyphal structures that place pressure on plant surfaces in order to infiltrate various tissues and begin forming a mycorrhizal association. Chlamydospores are globose to ellipsoid, and aseptate.[2] Spores range in size from about 100 to 350 μm in diameter. Spore walls are yellow to brown in color.[3] Spores arise from subtending hyphae that range from 12 to 25 μm in width. Hyphae are also cylindrical and lacking in pigmentation. Both young and mature spores are often evident on the sporocarp surface. The sporocarp of G. macrocarpum is a relatively fragile structure with other environmental components, such as soil, sometimes embedded in its surface.[2]
Ultrastructural studies indicate that two wall layers, containing fibrils, are present in spores. There is a slight separation zone present between the two wall layers. Spore contents are also indicated to be lipid globules from subtending hyphae as an energy source for the spores.[4]
Ecology
Glomus macrocarpum is a vesicular arbuscular mycorrhizal fungus that forms associations with many different plant types. The fungus grows in a hypogeous manner, just underneath the topsoil in various geographical locations and environments.[1] The fruiting season of G. macrocarpum occurs during the summer and fall months.[2] Until relatively recently, Glomus species were thought to be exclusively asexual organisms. However, studies have been conducted to analyze the presence of sex pheromone sensing proteins in some Glomus species. The presence of these sensing proteins is indicative that species in this genus may not be entirely asexual. However, the validity of a sexual process in Glomus species has not been confirmed.[5]