Rice is the world's most consumed cereal after wheat. It provides more than 50 percent
of the daily calories ingested by more than half of the world population. From the
beginning of time, rice grew as a wild crop, but today, most countries cultivate
varieties belonging to the Oryza type which has around twenty different
species. Only two out of the 20 species offer an agriculture interest for humans:
Oryza sativa: A common Asian rice
found in most producing countries, which originated in the Far East at the foot
of the Himalayas. O. sativa japonica grew on the Chinese side of the mountains
and O. sativa indica on the Indian side. The majority of the cultivated
varieties belong to this species, which is characterized by its plasticity and taste
Oryza glaberrima: An annual species
originating in West Africa, covering a large region extending from the central Delta
of the Niger River to Senegal.
Japonica is an irrigated rice of temperate zone, with medium or short grains,
also known as round grain, and is a rainfed lowland rice of warm tropical zones.
Indica is an irrigated rice of warm tropical zones, with long, thin and
Rice is a monocarpic annual plant, that grows to a height of 1–1.8 m, depending
on the variety and soil fertility. The grass has long, slender leaves 50–100
cm long and 2–2.5 cm broad. The wind pollinated flowers are produced as a
branched arching to pendulous inflorescence, 30–50 cm long. Each panicle has
50 to 300 flowers (floret or spikelet), which later form the grains. The seed is
a grain (caryopsis) 5–12 mm long and 2–3 mm thick.