Wild Relatives Of Rice: A Valuable Genetic Resource For Genomics And Breeding Research

Worldwide, more than 3.5 billion people depend on rice for more than 20% of their daily calories. Global rice demand is estimated to rise from 723 million tons in 2015 to 763 million tons in 2020 and to further increase to 852 million tons in 2035, an overall increase of 18% or 129 million tons in the next 20 years. World rice production has more than doubled from 257 million tones in 1966 to 680 million tons in 2010. This was mainly achieved through the application of principles of classical Mendelian genetics and conventional plant breeding. Further, rice productivity is continually threatened by several diseases (bacterial blight, blast, tungro virus, rice yellow mottle virus, sheath blight, etc.) and insects (plant hoppers, stemborer, and gall midge) including many abiotic stresses (drought, salinity, submergence, cold, heat, soil toxicities, etc.). To overcome these constraints particularly in the context of global climatic changes, there is urgent need to broaden the gene pool of rice; one of the options is to exploit wild species of Oryza which are reservoirs of useful genes/QTLs for rice improvement. Interspecific hybrids, alien introgression lines (AILs), chromosomal segmental substitution lines (CSSLs) have been produced. Several genes/QTLs governing agronomic traits have been transferred from wild species into rice, and a few of these tagged with molecular markers and used in marker-assisted selection (MAS). Some breeding lines of rice derived from wide crosses have been released as varieties.