Brachypodium distachyon
(purple false brome)

Preferred Scientific Name

• Brachypodium distachyon (L.) P. Beauv.

Preferred Common Name

• purple false brome

Other Scientific Names

• Bromus distachyos L.
• Trachynia distachya (L.) Link

International Common Names

• English: annual false brome; false brome; purple false brome; stiff-brome

Local Common Names

• China: er sui duan bing cao
• Finland: aroluste
• France: brachypode à deux épis; brachypode de Pau; brachypode de Phénicie; brachypode des bois; cutandie maritime; vulpie genouillée
• Germany: istrianer zwenke; zweiährige zwenke; zweigrannige zwenke
• Sweden: grusskafting

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Brachypodium
•                                 Species: Brachypodium distachyon

Brachypodium is a genus of about 18 species. About 15 species, among them Brachypodium distachyon, occur naturally in Eurasia, centered in the Mediterranean. Three species occur in the Western Hemisphere, centered in Mexico (Flora of North America Editorial Committee, 2016).

B. distachyon was first described by A.M.F.J. Palisot de Beauvois in 1812. The phylogenetic status of B. distachyon has been full of controversy. B. distachyon is sometimes treated as the only member of Trachynia Link. However, recently scientists have reclassified it into its own tribe Brachypodieae based upon cytological, anatomical and physiological studies (Hasterok et al., 2004; Flora of North America Editorial Committee, 2016; Gramene, 2016).

The Plant List (2016) includes at least 40 synonyms showing its previous inclusion in the genera Agropyron, Brachypodium, Bromus, Festuca, Secale, Trachynia, Triticum anmd Zerna.

Brachypodium is related to the major cereal grain species. But it is understood to be more closely related to the Triticeae (wheat, barley) than to the other cereals (Gramene, 2016).

Brachy is Greek for "short" and podion is Greek for "little foot". "Short footed" refers to the small pedicels of the spikelets (Watson and Dallwitz, 2016).

B. distachyon is an erect annual grass. Culms geniculately ascending, or decumbent; 3-40 cm long. The following is adapted from Cal-IPC (2016) and Clayton et al. (2016).

Leaves

Bright green or greenish-blue leaves; leaf-sheaths with slightly stiffened distinct hairs ascending from the surface. Ligule an eciliate membrane. Leaf-blades 1–12 cm long; 1–6 mm wide; glaucous. Leaf-blade surface with slightly stiffened distinct hairs ascending from the surface; sparsely hairy.

Inflorescence

Inflorescence composed of racemes. Racemes 1; single; bilateral; 2–8(–10) cm long; bearing 1–7 fertile spikelets on each. Spikelet packing broadside to rhachis. Spikelets solitary. Fertile spikelets pedicelled. Pedicels oblong; 0.5–1 mm long.

Fertile spikelets

Spikelets comprising 5–16 fertile florets; with diminished florets at the apex. Spikelets oblong; laterally compressed; 10–30 mm long; breaking up at maturity; disarticulating below each fertile floret.

Glumes

Glumes persistent; dissimilar; shorter than spikelet. Lower glume lanceolate; 5–6 mm long; 0.75 length of upper glume; coriaceous; without keels; 5–7 -veined. Lower glume lateral veins ribbed. Lower glume apex acute. Upper glume oblong; 7–8 mm long; 0.75 length of adjacent fertile lemma; coriaceous; without keels; 7 -veined. Upper glume lateral veins ribbed. Upper glume apex acute.

Florets

Fertile lemma oblong; laterally compressed; 8–10 mm long; coriaceous; glaucous; without keel; 7 -veined. Lemma surface glabrous, or pilose. Lemma margins ciliolate; hairy above. Lemma apex acute; awned; 1 -awned. Principal lemma awn 8–12 mm long overall. Apical sterile florets resembling fertile though underdeveloped.

Flowers

Lodicules 2; ciliate. Anthers 3; 0.5–1 mm long. Ovary pubescent on apex.

Fruits

Caryopsis with adherent pericarp; ellipsoid; hairy at apex, 7-8 mm long. Embryo 0.25 length of caryopsis. Hilum linear; 1 length of caryopsis (Cal-IPC, 2016; Clayton et al., 2016).

Soil drainage

• free

Soil reaction

• acid
• alkaline
• neutral
• very acid

Soil texture

• heavy
• light
• medium

Natural Dispersal

This species is spread by water (Cal-IPC, 2016).

Vector Transmission (Biotic)

Florets fall near the plant and can be dispersed by animals (Cal-IPC, 2016).

Accidental Introduction

The florets of B. distachyon can also be dispersed by vehicle tyres and human activities, especially in contaminated hay (Cal-IPC, 2016).

Intentional Introduction

Researchers use this species as a model for the grasses used to produce biomass, food, feed and forage (USDA-JGI, 2016).

It occurs broadly as an alien species throughout North America and has been reported as invasive in China, Chile, Australia and California (Calflora, 2016; PIER, 2016).

Brachypodium genera are invasive weeds that dominate areas where they grow (USDA Forest Service, 2003). In the USA, B. distachyon is a weed of urban bushland and of the western edge of the wheatbelt. It is specifically reported from California, Oregon, Texas, Colorado, Hawaii and New Jersey. Generally, it is under-reported, probably because of superficial similarity to Bromus species (Hussey et al, 1997; Gramene, 2016). B. distachyon is locally abundant in California. It seems to still be spreading in California, but probably at a relatively slow rate statewide. Regionally it can spread rapidly (Cal-IPC, 2016).

Impact on Habitats

B. distachyon can form dense stands that can change fire regimes and build up thick litter layers (Cal-IPC, 2016). An increase in woody vegetation and nonnative plant species in some habitats has resulted in less available prairie habitat overall.

Impact on Biodiversity

Cal-IPC (2016) evaluated the impact of B. distachyon on plant community composition, structure, and interactions as ‘Moderate’. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal, though establishment is generally dependent upon ecological disturbance. Ecological amplitude and distribution may range from limited to widespread. It can form dense stands in some locations, particularly in oak woodlands. These near monotypic stands can reduce diversity and prevent native species from establishing. The impact on higher trophic levels is evaluated as ‘Moderate’. The fibrous stems make it a poor forage for animals. The long awns can also injure animals (Cal-IPC, 2016).

It is recorded, among others, as being one of the most prominent nonnative species threatening the endangered Acanthomintha ilicifolia, competing for nutrients, light, water and space (US Fish and Wildlife Service, 2009). It is also noted as an invasive of concern to the protection of the endangered species Sibara filifolia (US Fish and Wildlife Service, 2006).  

B. distachyon can contribute to the loss of prairie habitat, and subsequently lead to habitat that is avoided by some butterflies and birds, such as the Taylor’s checkerspot butterflies (Euphydryas editha taylori) and streaked horned larks (Eremophila alpestris strigata) (US Fish and Wildlife Service, 2013).

Based on impact, invasiveness and distribution, Cal-IPC (2016) has given B. distachyon the alert status: ‘No Alert’.

• Proved invasive outside its native range
• Has a broad native range
• Pioneering in disturbed areas
• Tolerant of shade
• Fast growing

• Ecosystem change/ habitat alteration
• Modification of fire regime
• Modification of successional patterns
• Monoculture formation
• Reduced native biodiversity
• Threat to/ loss of native species

• Competition - monopolizing resources
• Competition - smothering
• Predation

• Highly likely to be transported internationally deliberately
• Difficult to identify/detect as a commodity contaminant

Economic Value

B. distachyon is used by researchers as a model for the grasses used to produce biomass, food, feed and forage. The species has many qualities that make it an excellent model organism for functional genomics research in temperate grasses, cereals, and dedicated biofuel crops. These attributes include the relatively small size of its genome which makes it useful for genetic mapping and sequencing. It has diploid accessions and a series of polyploid accessions. It is small sized, has a short lifecycle and it is self compatible. As a weed it has simple growth requirements (USDA-JGI, 2016).

Studies in B. distachyon have provided new insight into the structure and physiology of plant cell walls, the development and chemical composition of endosperm, and the genetic basis for cold tolerance. Recent work on auxin transport has also uncovered mechanisms that apply to all angiosperms other than Arabidopsis (Kellogg, 2015).

The species is a poor forage grass for livestock (DiTomaso et al., 2013).