ABSTRACT
The predominant cultivated species of rice ( Oryza sativa L.) was probably first domesticated in Southeast Asia (1 ). Archeological evidence of rice cultivation in China 7000 years ago has been reported (2). Three ecogeographic races of 0. sativa have evolved. Indica is the tropical race, Japonica is the temperate race, and Javanica, believed to have evolved in Indonesia, is intermediate between Indica and Japonica (3). In addition to the partial sterility oflndica X Japonica hybrids, climatic adaptation, and morphological characteristics, certain general quality characteristics have been associated with the Indica and Japonica races. Indica types generally have long slender grains and cook dry and flaky, whereas Japonica types have short round grains and cook moist and sticky. Hybridization between types and selection for certain grain shape and quality characteristics have made this classification of quality less definitive and useful. Genetic studies of isozyme polymorphisms indicated that modern U.S. rice cultivars were grouped with the classical Japonica and Javanica types and were distinct from the classical Indicas (4,5). However, the grain shape and cooking characteristics of U.S. long-grain cultivars, as will be discussed later, are not typical of classical Japonicas.
