Asian cultivated rice (Oryza sativa) only. Stage: flowering to maturity. O. sativa is classified into two major cultivar groups, indica and japonica, based traditionally on morphological and grain characteristics. Other groups have also been recognized but since the variation in morphological features among cultivars is continuous, it is often difficult to make an accurate classification. Isozyme data and molecular data are generating new insights but are not entirely consistent with the morphological classifications (Glaszmann 1987); for example, it is quite common for accessions to be classified as indica by morphology but japonica by isozymes. Both systems are therefore provided here, although this may need to be revised as new information is obtained. The traditional morphological classification recognizes four major groups.