‘Grass is the forgiveness of Nature -her constant benediction’ ~ John James Ingalls
Humans discovered cereal grasses over 10,000 years ago and explored their unparalleled use as food, which turned out to be a prerequisite for civilizations in time. Out of the 7000 plant species cultivated for food*, the three ‘king makers’ of grasses – Wheat, Rice and Maize – supply 50 % of the world food and they comes first in the global production of crops together with another crop-grass, Sugarcane (Saccharum officinarum L.)
- Wheat (Triticum aestivum), the ‘king of cereals’
- Barley (Hordeum vulgare), the first cultivated crop
- Corn or Maize (Zea mays), the ‘queen of cereals’
- Rice (Oryza sativa), the most consumed food
A perspective on Grass Classification
Owing to economic and ecological importance of the family many attempts have been made for obtaining a useful classification for the grasses. It is seen that there are four successive revolutionary periods, which is marked by the introduction of anatomical, physiological and molecular characters to supplement gross morphology in classification.
Brown(1814) made the first scientific division, and he classified grasses into two “tribes” (subfamilies), viz., “Poaceae” (Pooideae) and “Paniceae”(Panicoideae), which was based on morphology of spikelet characters.
The ‘New systematics’ which are primarily based on size of chromosomes, orientation and size of the first seedling leaf, as well as anatomical features eventually lead to the separation of chloridoid grasses from the pooids.Stebbins and Crampton (1961) suggested a classification system, and it has been mostly set up on the basis of anatomical, cytological and physiological features rather than traditional morphological characters such as the nature of the inflorescences and spikelets, and it has recognized into 6 subfamilies.
A comprehensive system of Clayton and Renvoize (1986) recognised 6 subfamilies (Bambusoideae, Centothecoideae, Pooideae, Arundinoideae, Chloridoideae and Panicoideae) and is widely used in Grass systematic studies now. It has presented predictive evolutionary relationships at the tribal and generic level, which have been relied upon by subsequent workers for their studies on evolution and phylogenetic reconstructions.
The phylogenetic classifications (GPWG, 2000; 2001, 2012 & Soreng et al, 2015) recognized 12 subfamilies, 51 tribes, 80 subtribes, and 771 genera in approximately 12074 species within the family based on a combined analysis of molecular as well as morphological characters. Here, the system recognised three species-poor lineages (Anomochlooideae, Pharoideae and Puelioideae) that are successively sister to all other grasses and placed the bulk of grass diversity in two main clades, known by their acronyms as BOP (Bambusoideae, Oryzoideae and Pooideae) and PACMAD (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae and Danthonioideae).
Epilogue: The current classification system (GPWG I , II & Soreng et al, 2015) addresses only about 80% of representative World grass genera/taxa. Many narrowly distributed asian taxa belonging to Andropogoneae, the largest tribe in the family, are poorly represented ?!
Cladogram showing different clades and subfamilies. Representative genera/species shown in parenthesis (GPWG, 2012)
‘The Tree of Grass’ : Phylogenetic relationships of ancestral groups, subfamilies and tribes of family Poaceae (Soreng et al, 2015)
GrassWorld: An online information system of the world’s grasses
Grass Genera of the World by L. Watson and M. J. Dallwitz
GrassBase: Species descriptions of World Grass Flora by W.D. Clayton, et. al.
e-Monocot: An online resource for Monocot plants.
Tropicos : More links on grasses and New World grasses
Bamboo Identification: On-line resource for Bamboos
Grass Phylogeny Working Group(GPWG): Research on grass classification
Grass India: A photo essay on sedges & grasses of India
GrassPortal: Databases for grass systematics
Herbarium Catalogue of RBG, Kew