Cereals

Abstract

Cereals occupy maximum hectares of land and hold world’s largest grain production. Rice, wheat, and maize account for 80% of the grain produced in the world. The major distribution areas of wild species of cereals in India are the Western Himalayas, the northeastern region, and eastern peninsular tracts. Archeological and historical evidence reveal the region extending from Northeast Hills in India to mountain ranges of Southeast Asia and South-West China to be the primary center of origin of Oryza sativa L. India has abundant wild species genetic resources of rice spread all over the subcontinent except for the western arid and semi-arid plains (Fig. 4.1). It is particularly rich for Oryza nivara Sharma & Shastry, O. rufipogon Griff., O. officinalis Wall. ex Watt, O. malamphuzhensis and O. granulata Nees & Arn. ex Watt. (Fig. 4.1). Most species are found in ditches, ponds, and paddy fields; O. nivara is largely found in the Deccan Plateau (Fig. 4.2a). The natural hybrid population (O. sativa ssp. spontanea) of O. sativa with wild relatives, O. nivara, and O. rufipogon in rice field is found all over South and Southeast Asia. Maximum diversity in Oryza species occurs in the peninsular tract of eastern part of the country with O. nivara (annual), O. rufipogon (perennial), and weedy O. spontanea types in indica cultivars. In addition, Porteresia coarctata (Roxb.) Tateoka (= O. coarctata), a tetraploid species, also exists in India and is found in the tidal swamps of Sunderbans and the Godavari delta. The other members of Oryzeae of potential use are Hygroryza aristata (Retz.) Nees, Leersia hexandra Swartz, and L. hackelii Keng, a cold-tolerant species.