Megathyrsus maximus
Family :
Famille :
Poaceae
Synonym(s) :
Synonyme(s) :
Panicum maximum Jacq. (Wiersema & León 2016; CABI 2023; ITIS 2023; USDA-ARS 2023)
Urochloa maxima (Jacq.) R. D. Webster (CABI 2023; ITIS 2023; FNA 1993+; USDA-ARS 2023)
Panicum hirsutissimum Steud. (CABI 2023; ITIS 2023; USDA-ARS 2023)
Common Name(s) :
Nom(s) commun(s) :
Guinea grass
(English) (FNA 1993+; UPOV 2011+, Wiersema & León 2016; AOSA 2023; CABI 2023; USDA-ARS 2023)
Herbe de Guinée (French) (UPOV 2011+; Wiersema & León 2016; CABI 2023; USDA-ARS 2023)
Green panic grass (English) (UPOV 2011+; Wiersema & León 2016; AOSA 2023; USDA-ARS 2023)
Da shu 大黍 (Chinese) (FOC 1994+)
Guineagras (German) (UPOV 2011+; Wiersema & León 2016; CABI 2023; USDA-ARS 2023)
Capim-colonião (Portuguese) (Wiersema & León 2016; USDA-ARS 2023)
Mijo de Guinea (Spanish) (UPOV 2011+; Wiersema & León 2016; USDA-ARS 2023)
Megathyrsus maximus spikelets
Megathyrsus maximus spikelets
Megathyrsus maximus spikelets
Megathyrsus maximus florets
Megathyrsus maximus florets
Megathyrsus maximus floret, lemma profile
Megathyrsus maximus floret, close up
Megathyrsus maximus dissected spikelet: a. lower (1st) glume, b. upper (2nd) glume, c. sterile floret lemma, d. sterile floret palea, e. fertile floret lemma
Megathyrsus maximus caryopses, embryo view, lateral view, and hilum view (left to right)
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Overview
Aperçu
Regulation :
Remarques Réglementation:
Regulation Notes:
Distribution :
Répartition :
Megathyrsus maximus is native to Africa and the Arabian Peninsula (USDA-NCRS 2023), but is naturalized throughout the tropics (FNA 1993+; Rhodes et al. 2021). This species is now present in China, Australia, New Zealand, Southeast Asia, India, South America, the Caribbean, Pacific Islands, Japan, the Middle East, Mexico and the southern United States (Rhodes et al. 2021; POWO 2023; USDA-NCRS 2023). M. maximus has been found in Spain, Sicily and Czechoslovakia in Europe, and is not present in Canada (Brouillet et al. 2010+; POWO 2023).
Habitat and Crop Association :
Habitat et Cultures Associées :
M. maximus is found in grassland and savanna that receive at least 1 meter of total rainfall with a short dry season (Holm et al. 1991; Rhodes et al. 2021). The species can survive drought or flooding for short periods but is limited by cold temperatures (Holm et al. 1991; Rhodes et al. 2021). It appears to prefer fertile soils in the understory of nitrogen-fixing tree species (Pietrese et al. 1997; Ellsworth et al. 2013; Rhodes et al. 2021).
It is a prominent weed of Saccharum officinarum L. (sugarcane) in Cuba, Hawai’I, South Africa, Australia, Costa Rica, Mexico and Taiwan (Holm et al. 1991). It can infest other tropical crops such as: Musa L. spp. (banana), Theobroma cacao L. (cacao), Coffea L. spp. (coffee), Zea mays L. subsp. mays (corn), Gossypium hirsutum L. (cotton), Cocos nucifera L. (coconut), Ananas comosus (L.) Merr. (pineapple), Citrus L. spp. (citrus), Oryza sativa L. (rice), Arachis hypogaea L. (peanuts), Agave sisalana Perr. (sisal hemp), and Camellia sinensis (L.) Kuntze (tea) (Holm et al. 1991).
M. maximus may become a dominant species when infested fields are abandoned, e.g., cattle pasture, S. officinarum and A. comosa fields in Hawai’i (Ellsworth et al. 2013; Trauernicht et al. 2015). This species can also spread into adjacent disturbed sites, fallow fields, native grasslands, streambanks, tropical forest understory and roadsides (FNA 1993+; Trauernicht et al. 2015; Rhodes et al. 2021).
Economic Use, cultivation area, and Weed Association :
Utilisation économique, zone de culture et association de mauvaises herbes :
M. maximus is considered to be one of the most nutritious forages for beef production in tropical climates (Holm et al. 1991; Aganga and Tshwenyane 2004). This grass has been historically beneficial to countries outside of Africa including lndia, Guatemala, Colombia, Mexico, Barbados and Jamaica (Parsons 1972). Improved forage breeding programs continue in India, Brazil, Japan, and Mexico with cultivars adapted to local conditions (Rhodes et al. 2021). This species has also been used for revegetation and erosion control (Aganga and Tshwenyane 2004; Ho et al. 2016).
Duration of Life Cycle :
Durée du cycle vital:
Perennial
Dispersal Unit Type :
Type d’unité de dispersion :
Spikelet
General Information
RENSEIGNEMENTS GÉNÉRAUX
The species has been split into three varieties (USDA-ARS 2023), and cultivars have been developed from two varieties (Simon and Alfonso 2011):
- M. maximus (Jacq.) B. K. Simon & S. W. L. Jacobs var. maximus; leaf collar and spikelets glabrous; includes cultivars Gatton, Makueni, Riversdale, Embu, Hamil
- M. maximus var. coloratus (C.T.White) B. K. Simon & S. W. L. Jacobs; leaf collar hairy, spikelets glabrous; no cultivars recorded
- M. maximus var. pubiglumis (K.Scum.) B. K. Simon & S. W. L. Jacobs; leaf collar glabrous, spikelets hairy; cultivar Petrie
M. maximus generally sets seed without fertilization (apomixis), creating populations with low genetic diversity but well-adapted to the local environment (Holm et al. 1991). Many countries breed localized cultivars of M. maximus, broadly categorized into tall and short forms, to maximize production in a particular climate (Rhodes et al. 2021; Gaskin et al. 2022). Each inflorescence of Megathyrsus maximus can produce seed throughout the year, ensuring a consistent supply of seed (Holm et al. 1991; Rhodes et al. 2021). Holm et al. (1991) reported that 9000 seeds were produced by one plant. Seed is dispersed via birds, arthropods, and machinery from infested fields (Rhodes et al. 2021).
Fresh seeds of M. maximus are dormant, and techniques to break dormancy may depend on the environment it grew in (Cabrera et al. 2020). Chemical scarification was effective for seeds produced in the United States, while thermal treatments were successful in Brazil (Cabrera et al. 2020). Retention of the glumes on shed florets may also be a barrier to germination (Cabrera et val. 2020).
The traits that make M. maximus a valuable forage species, such as rapid growth, tolerance of herbivory, environmental adaptation and reproductive plasticity also makes it an effective invader (Rhodes et al. 2021; Gaskin et al. 2022). Conversion of natural areas to agriculture, and abandonment of fields promotes invasion of non-native species, including M. maximus (Ellsworth et al. 2013; Trauernicht et al. 2015). This species can spread into natural areas and become the dominant species in abandoned fields (Ellsworth et al. 2013). Flammable litter from M. maximus increases wildfire risk (Ellsworth et al. 2013; Trauernicht et al. 2015). A self-perpetuating cycle between wildfires and fire-adapted M. maximus can develop, increasing both fire frequency and intensity (Ellsworth et al. 2013).
In Hawai’i, an estimated 90% of the over 760 000 hectares of agricultural land are unmanaged and now dominated by non-native grasses (Trauernicht 2015). Dry M. maximus-dominated fields near Lahaina, Maui exacerbated the intensity, area and damage of wildfires in August of 2023 (Shingler 2023).
.Identification
Identification
-
Spikelet
Size
- Spikelet length*: 3.1 – 3.9 mm; width: 1.0 – 1.2 mm
*Note: minimum and maximum based on 10 spikelets in normal range of this species using image measurement protocol (ISMA 2020).
Spikelet size from literature:
• Spikelet length: 2.5 – 4 mm (Holm et al. 1991)
• Spikelet length: 2.7 – 3.6 mm; width: 0.9 – 1.1 mm (FNA 1993+)
• Spikelet length: (2.5–)3 – 4.5(–5) mm (Simon and Alfonso 2023)Glume size from literature:
• Lower (1st ) glume length: 0.8 – 1.2 mm, upper (2nd ) glume length: 2.1 – 3.5 mm (FNA 1993+)
• The lower (1st) glume covers ¼ – ½ of the spikelet; the upper (2nd) glume covers the length of the spikelet.Shape
- Spikelet oblong or elongate egg-shaped
- The lower (1st) glume is egg-shaped and wraps around the spikelet
- The upper (2nd) glume is elongate egg-shaped
Surface Texture
- The lower (1st) glume is 1 – 3 nerved; the upper glume (2nd) is 5 nerved (FNA 1993+)
- Spikelet surface generally glabrous, may be pubescent
- Glumes have a stiff papery consistency
Colour
- Spikelet shiny brownish-yellow when mature, many have purple patches
Other Features
- The spikelet is composed of two glumes, a sterile lower floret and a fertile upper floret.
- Disarticulation of spikelets occurs below the glumes, and the spikelet is shed intact (Smith 1970).
Megathyrsus maximus spikelets
-
Floret (fertile)
Size
- Fertile floret length*: 2.5 – 2.7 mm; width: 0.9 – 1.0 mm
*Note: minimum and maximum based on 10 florets in normal range of this species using image measurement protocol (ISMA 2020).
Floret size from literature:
• Fertile floret length: up to 3 mm (Holm et al. 1991)
• Fertile floret length: 1.9 – 2.4 mm (FNA 1993+)
• Fertile floret length: 1.9 – 5 mm (Simon and Alfonso 2023)Shape
- Floret elongated oval or elongated egg-shaped with one pointed end
- Fertile lemma is pinched past the palea, the pointed tip curved down towards the palea
- Fertile palea flat or bulging at either end
Surface Texture
- The fertile floret has a hard, inflexible lemma and palea
- Fertile lemma and palea transversely ridged; ridges appear warty tuberculate under 30x magnification
- Fertile palea sides smooth and glossy, may or may not be exposed in mature florets
- Fertile lemma has a tuft of short hairs at the pointed end
Colour
- Mature fertile floret is shiny yellow or yellow-brown coloured, may have a patch of purple at the pointed end, or purple streaks
- Immature florets white or pale yellow coloured
Other Features
- The fertile floret may also be called the upper floret
Megathyrsus maximus florets
-
Floret (sterile)
Size
- Sterile floret length: 2.1 – 3.5 mm (FNA 1993+)
Shape
- Sterile floret is oblong or elongate egg-shaped with one pointed end, plano-convex in 3D view.
- Sterile lemma may be convex or flat
Surface Texture
- The sterile floret has a flexible, leathery lemma and a translucent (membranous) palea
- Sterile lemma surface smooth or pubescent with five longitudinal, slightly raised nerves
Colour
- Sterile floret brownish-yellow when mature, may have purple patches
Other Features
- Sterile florets are generally staminate (FNA 1993+)
Megathyrsus maximus dissected spikelet: a. lower (1st) glume, b. upper (2nd) glume, c. sterile floret lemma, d. sterile floret palea, e. fertile floret lemma
-
Caryopsis
Size
- Caryopsis length: Caryopsis 3 mm; width: 1 mm (Holm et al. 1991)
Shape
- Caryopsis is oval shaped, compressed in 3D view
Surface Texture
- Caryopsis surface is smooth
Colour
- Caryopsis is shiny yellow coloured
Other Features
- The hilum is a reddish oval on the opposite side of the embryo
Megathyrsus maximus caryopses, embryo view, lateral view, and hilum view (left to right)
-
Embryo
Size
- Embryo partially fills the seed
- Embryo generally covers half of the caryopsis
Shape
- Embryo is oval shaped
Endosperm
- Endosperm is hard and opaque light brown coloured
Other Features
- Embryo position lateral
Megathyrsus maximus caryopses, embryo view, lateral view, and hilum view (left to right)
Identification Tips
CONSEILS POUR L’IDENTIFICATION
Megathyrsus maximus is in the Paniceae tribe of Poaceae with approximately 1000 species, generally with a tropical distribution (FNA 1993+). Genera in this tribe include: Cenchrus, Digitaria, Echinochloa, Panicum and Setaria. The common features of these genera include:
- Generally dispersed as spikelets
- Spikelets with 2 florets
- One floret is fertile and inflexible, the rest generally sterile and flexible with the sterile lemma similar to the upper (2nd) spikelet glume
- A germination flap (U-shaped crack at the base of the fertile lemma) is present (FNA 1993+)
The genus Megathyrsus is characterized by:
- Upper (2nd) glume and sterile lemma 5-nerved without cross-links
- Florets yellow coloured, elongate oval shaped
- Fertile floret surface generally roughened with both tubercules and transverse ridges
Megathyrsus maximus spikelets
Additional Botany Information
AUTRES RENSEIGNEMENTS BOTANIQUES
Flowers/Inflorescence
- Inflorescence branches in whorls (rings) around the flower stalk.
- Inflorescence 20 – 65 cm long, open, generally more than 20 primary branches (FNA 1993+).
- Spikelets are solitary, paired or in a group of three on the inflorescence branches (FNA 1993+).
- Anthers large relative to floret size (1.2-2.2 mm, FNA 1993+), orange when fresh, dark purple coloured when dried.
Vegetative Features
- Plants can grow to up to 4 m tall (Holm et al. 1991)
- Stems can grow in tufts from thin, fibrous roots and short rhizomes, and can also produce roots from stem nodes (FNA 1993+)
- Leaves are flat, (15)30 – -75(100) cm long and 10-35 mm wide, may be smooth or hairy (FNA 1993+)
Similar Species
ESPÈCES SEMBLABLES
Similar species are based on a study of seed morphology of various species, and those with similar dispersal units are identified. The study is limited by physical specimen and literature availability at the time of examination, and possibly impacted by the subjectivity of the authors based on their knowledge and experience. Providing similar species information for seed identification is to make users aware of similarities that could possibly result in misidentification.
Megathyrsus infestus (Andersson) B. K. Simon & S. W. L. Jacobs
M. infestus is native to eastern and southern Africa, and has not been recorded outside of Africa (USDA-ARS 2023). This species is generally shorter (up to 200 cm tall, Hyde et al. 2023), with an oblong-shaped inflorescence, spikelets generally smaller (2.5 – 4 mm) with a short lower (1st)) glume covering 1/4 – 1/3 of the spikelet length (Hyde et al. 2023). M. maximus has generally larger spikelets (length*: 3.1 – 3.9 mm) with the lower (1st) glume covering 1/3 – 1/2 of the spikelet length (Hyde et al. 2023). Note that M. maximus and M. infestus hybrids have been found in East Africa (Gaskin et al. 2022).
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Megathyrsus maximus floret, lemma profile
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Megathyrsus maximus floret, close up
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Megathyrsus maximus dissected spikelet: a. lower (1st) glume, b. upper (2nd) glume, c. sterile floret lemma, d. sterile floret palea, e. fertile floret lemma
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Megathyrsus maximus
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Megathyrsus maximus caryopses, embryo view, lateral view, and hilum view (left to right)
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Reference(s)
Référence(s)
Aganga, A. A. and Tshwenyane, S. 2004. Potentials of Guinea Grass (Panicum maximum) as Forage Crop in Livestock Production. Pakistan Journal of Nutrition 3: 1-4.
Association of Official Seed Analysts (AOSA). 2023. Rules for Testing Seeds, Vol. 3: Uniform Classification of Weed and Crop Seeds. Association of Official Seed Analysts, Wichita, KS, USA.
Brouillet, L., Coursol, F., Meades, S. J., Favreau, M., Anions, M., Bélisle, P. and Desmet, P. 2010+. VASCAN, the database of vascular plants of Canada. http://data.canadensys.net/vascan/ Accessed November 3, 2023.
Cabrera, D. C., Sobrero, M.T., Chaila, S., Pece, M. 2020. Effect of environmental factors on the germination of Megathyrsus maximus: an invasive weed in sugarcane in Argentina. Planta Daninha. https://doi.org/10.1590/S0100-83582020380100054 Accessed November 3, 2023.
Centre for Agriculture and Bioscience International (CABI). 2023. Invasive Species Compendium, CAB International, Wallingford, UK. https://www.cabidigitallibrary.org/journal/cabicompendium Accessed November 22, 2023.
Ellsworth, L. M., Litton, C. M., Taylor, A. D. and Kauffman, J. B. 2013. Spatial and temporal variability of guinea grass (Megathyrsus maximus) fuel loads and moisture on Oahu, Hawaii. International Journal of Wildland Fire 22: 1083–1092.
Flora of China (FOC) 1994+. Megathyrsus maximus Vol. 22 Page 505, 506 (English edition). http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200025820 Accessed November 22, 2023.
Flora of North America (FNA) Editorial Committee, eds. 1993+. Flora of North America North of Mexico [Online]. 22+ vols. New York and Oxford. http://beta.floranorthamerica.org Accessed November 3, 2023
Gaskin, J. F. , Goolsby, J. A., Bon, M. C., Cristofaro, M. and Calatayud, P. A. 2022. Identifying the geographic origins of invasive Megathyrsus maximus in the United States using molecular data. Invasive Plant Science and Management 15: 67–71.
Holm, L. G., Plucknett, D. L., Pancho, J. V. and Herberger, J. P. 1991. The World’s Worst Weeds, Distribution and Biology. Krieger Publishing, Florida. 609 pp.
Hyde, M. A., Wursten, B. T., Ballings, P. and Coates Palgrave, M., 2023. Flora of Zimbabwe. https://www.zimbabweflora.co.zw/index.php November 8, 2023.
Integrated Taxonomic Information System (ITIS). 2023. https://www.itis.gov/ Accessed November 22, 2023.
Parsons, J. J. 1972. Spread of African pasture grasses to the American tropics. Journal of Range Management 25:12–17.
Pietrese, P. A., Rethman, N. F. G. and van Bosch, J. 1997. Production, water use efficiency and quality of four cultivars of Panicum maximum at different levels of nitrogen fertilisation. Tropical Grassland 31: 117-123.
Plants of the World Online (POWO) 2023. Facilitated by the Royal Botanic Gardens, Kew. http://www.plantsoftheworldonline.org/ Accessed November 3, 2023.
Rhodes, A. C., Plowes, R. M., Goolsby, J. A., Gaskin, J. F., Musyoka, B., Calatayud, P. A., Cristofaro, M., Grahmann, E. D., Martins, D. J. and Gilbert, L. E. 2021. The dilemma of Guinea grass (Megathyrsus maximus): a valued pasture grass and a highly invasive species. Biological Invasions 23: 3653–3669.
Shingler, B. 2023. “Why Maui’s deadly wildfires spread so quickly” CBC News https://www.cbc.ca/news/climate/maui-fires-explainer-1.6932886 Accessed November 6, 2023.
Simon, B. K. and Alfonso, Y. 2011. AusGrass2, http://ausgrass2.myspecies.info/ Accessed November 8, 2023.
Smith, C. J. 1970. Seed dormancy in Sabi panicum. Proceedings of the International Seed Testing Association 36: 81-97.
The International Union for the Protection of New Varieties of Plants (UPOV). 2011+. GENIE DATABASE. https://www.upov.int/genie/details.xhtml?cropId=8125 Accessed November 22, 2023.
Trauernicht, C., Pickett, E., Giardina, C. P., Litton, C. M., Cordell, S. and Beavers, A. 2015. The contemporary scale and context of wildfire in Hawai’i. Pacific Science 69: 427-444.
U.S. Department of Agriculture-Agricultural Research Services (USDA-ARS). 2023. Germplasm Resources Information Network (GRIN), https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch Accessed November 8, 2023.
Wiersema, H. and León, B. 2016. World Economic Plants. Available from: VitalSource Bookshelf (2nd Edition). Taylor & Francis.