Rice is grown in many countries. In Asia, it is eaten as a staple food.
Non-sticky long-grain rice (Oryza sativa ssp. Indica) is one of the most important groups of rice and includes patna rice and basmati rice. The other major category of rice is short-grain sticky rice, also called short-grain glutinous rice. Morphologically, medium-grain rice is the third subspecies — based on its length-to-width ratio, it is somewhere in between short-grain and long-grain rice. There is no wild form for the species Oryza sativa as this species was produced by breeding other varieties. Wild rice sold in supermarkets isn’t in the genus Oryza but instead in the genus Zizania.
From Wikipedia: “Rice is the seed of the grass species Oryza sativa (Asian rice) or Oryza glaberrima (African rice). As a cereal grain, it is the most widely consumed staple food for a large part of the world's human population, especially in Asia. It is the agricultural commodity with the third-highest worldwide production (rice, 741.5 million tonnes in 2014), after sugarcane (1.9 billion tonnes) and maize (1.0 billion tonnes).”
“The traditional method for cultivating rice is flooding the fields while, or after, setting the young seedlings. This simple method requires sound planning and servicing of the water damming and channeling, but reduces the "growing" of less robust weed and pest plants that have no submerged "growing" state, and deters vermin. While flooding is not mandatory for the cultivation of rice, all other methods of irrigation require higher effort in weed and pest control during "growing" periods and a different approach for fertilizing the soil.”
“The varieties of rice are typically classified as long-, medium-, and short-grained. The grains of long-grain rice (high in amylose) tend to remain intact after cooking; medium-grain rice (high in amylopectin) becomes more sticky. Medium-grain rice is used for sweet dishes, for risotto in Italy, and many rice dishes, such as arròs negre, in Spain. Some varieties of long-grain rice that are high in amylopectin, known as Thai Sticky rice, are usually steamed. A stickier medium-grain rice is used for sushi; the stickiness allows rice to hold its shape when molded. Medium-grain rice is used extensively in Japan, including to accompany savoury dishes, where it is usually served plain in a separate dish. Short-grain rice is often used for rice pudding.”
“Cooked, unenriched, white, long-grained rice is composed of 68% water, 28% carbohydrates, 3% protein, and negligible fat (table). In a 100 gram serving, it provides 130 calories and contains no micronutrients in significant amounts, with all less than 10% of the Daily Value ... Cooked, white, short-grained rice also provides 130 calories and contains moderate amounts of B vitamins, iron, and manganese (10–17% DV) per 100 gram amount.
A detailed analysis of nutrient content of rice suggests that the nutrition value of rice varies based on a number of factors. It depends on the strain of rice, that is between white, brown, red, and black (or purple) varieties of rice – each prevalent in different parts of the world. It also depends on nutrient quality of the soil rice is grown in, whether and how the rice is polished or processed, the manner it is enriched, and how it is prepared before consumption.
Rice is the staple food of over half the world's population. It is the predominant dietary energy source for 17 countries in Asia and the Pacific, 9 countries in North and South America and 8 countries in Africa. Rice provides 20% of the world’s dietary energy supply, while wheat supplies 19% and maize (corn) 5%.”
“Since sizable portions of sugarcane and maize crops are used for purposes other than human consumption, rice is the most important grain with regard to human nutrition and caloric intake, providing more than one-fifth of the calories consumed worldwide by humans. There are many varieties of rice and culinary preferences tend to vary regionally.”