**2.1 Origin**

The most grown and utilizing species of rice are glaberrima (known as African rice) and *Oryza sativa* (known as Asian rice). These are considered as a progenitor of the Oryza species. It is estimated that *Oryza sativa* is grown approximately on the area of 1200 km belt including the areas of Himalaya mountains, areas near the Gangs river of India, Bangladesh, Bhutan, northern Burma, crossing the areas of Thailand, passing through Laos and Vietnam, it covers the some area of china as well. The Asian rice is mostly cultivated in south east Asia and south region. Due to the large belt of rice cultivation, the exact origin of domestication and evolution of related species and intermediates of the rice could not find. The domestication of Asian rice took place at many places in various times in south Asian regions [6]. On other hand, O glaberrima was known to be originated from the Niger river areas in west Africa, almost 3000 years before. The wild crop *Oryza barthi* is considered as its progenitor. After that *Oryza glaberrima* was grown in Liberia [7].

*Rice: Worldwide Production, Utilization, Problems Occurring Due to Climate Changes… DOI: http://dx.doi.org/10.5772/intechopen.96750*

#### **2.2 Domestication and diversification**

There were two ways used for the domestication of the rice cultivation in China and India. In Yangtze japonica, the traits for the domestication were utilized in the beginning and this process was accomplished in China 6,000 to 6,500 years ago. But it was completed approximately after 20,000 years in India. At that time, the Chinese rice was hybridized. When farming trends increase then the growing of rice also moved to the nearby areas among the populations. In this way the rice, the spreading of the rice take place from china to its south regions such as Austronesian and Sino-Tibetan groups. On other hand, In south regions of Asia the distribution of the rice take place after Dravidian and Indo-Aryan have gotten the whole quantity of rice from the northern India [8]. Rice Diversification and domestication processes were exposed to with the help of archaeology, ecology and genetics. Archaeology discovers the evolutionary dates of rice were 4000 BC in india and 5000 BC in china. First detailed study was conducted in Hastinapur city of India on carbonized grains of rice at 1100–750 BC. The samples were taken from Atranjikera a city of Uttar Pradesh almost 1500–1000 BC. After that the cultivation of rice started spreading in different countries of the words such as its cultivation was introduced to the Japan 100-300 BC, west areas of India at 2000 BC, and Philippines and Malaysia by 1400 BC [9].

#### **2.3 Distribution of rice**

Paddy rice are those rice which do not contain husk on their surface and brown rice are those which contained any outer surface on it. This can be removed by the milling. After that the rice are polished to obtain the white rice. Rice are mostly grown on the flat lands, delta areas and near the rivers, but it is very difficult to describe the specific environmental conditions and areas for its growth. The countries containing the warm temperatures or subtropical climates give the maximum yields of the rice. The rice yield varies in all over the world according to the latitudes such as 50o N, 45o N and 39o S for China, Japan and Australia accordingly. The areas present at the latitude of 40o S and 45o N are considered as extensive rice cultivating areas. Highest yield is observed in between 30o N to 45o N of equators. It is also being grown in those areas which are present at the below levels of sea i.e., Kerala. In Jammu and Kashmir, the rice is also cultivated at 1979 m altitudes. It can also be cultivated in the deep and shallow water while rainy season is on peak [10]. The rice cultivation in widely range is due to its various varieties according to their origin. Rice can be grown in all kinds of environments depending on the nature of the cultivars. Mostly varieties can be grown in the areas where irrigation waters are available. Furthermore, some varieties of rice are also available, which grow in specific season and at specific lands.

#### **2.4 Civilization due to rice**

Rice play an important role in the human diet from the beginning. It has enhanced the civilization and boosted the national economy in each country growing the rice by exporting it to the rest of countries. It plays important role to fulfill the dietary requirements in increasing population, their culture and civilizations. Rice was swamp grass of the semitropical areas, before its cultivation on large levels in agriculture sectors. Then it became the additional food to the peoples of the tribes, who were dependent on the fishing, hunting and other wild foods. Its yield is less on the local level, but the implementation of the management practices

like conservation of nutrients and water, and application of soil fertilizers, weeding and tillage practices, and selection of good varieties of the rice has boosted its yield on greater extend. The maximum rice crop can be yielded by utilization and managements of good practices, which are helpful to mitigate the problems of rice growth. Hence after these adaptations, there was great influence in rice yield per acre, rice growing areas and different cropping systems were developed. In this way, civilization was started flourishing throughout the Asia sub-continent. Now, Asian countries are contributing in their economy and meeting the surplus requirements of the population [11].
