Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: March 5, 2002
Publication Date: N/A
Interpretive Summary: Interpretive summary not required.
Technical Abstract: Cultivated rice (Oryza sativa L.) is a diploid species with 24 chromosomes. O. sativa chromosomes have been designated as the A-genome with the other 23 Oryza species designated as either AA, BB, CC, BBCC, CCDD, EE, FF, GG, HHJJ or HHKK. Rice chromosomes are numbered from one to twelve with chromosome one being the longest and chromosome twelve the shortest. The Rice Genetics Cooperative coordinates and monitors gene symbols with new symbols and revised linkage maps being published in the annual Rice Genetics Newsletter. Genes can be mapped to chromosome using trisomic plants, plants having 25 chromosomes (2n+1=25). Worldwide, three complete sets of rice trisomics are available. Rice can be further characterized and introgression of Oryza species DNA into O. sativa can be followed utilizing in situ hybridization techniques (FISH, GISH, fiber-FISH). Use of induced mutations expanded the field of rice genetics with efforts focused on production of "useful" mutants, such as shorter plant, earlier maturity, waxy endosperm, decreased phytic acid and increased herbicide tolerance. The induced mutant semidwarfing gene (sd1) in Calrose 76 has been used as the ancestral semi-dwarfing source for development of 20 improved semidwarf cultivars. "Breeding tool" mutants have been developed including gold hull and light green hull mutants for use in cultivar identification, and elongated uppermost internode mutants for use in hybrid rice seed production. Most recently, "knockout mutants" have been identified to determine the gene sequence which codes for a particular gene function. The history of hybrid rice is reviewed, including a description of the 3-line, 2-line and 1-line (apomixis) methods of producing hybrid seed.