Abstract
From the viewpoint of ecological classifiaction, Linne's species consists of ecospecies, ecotypes and ecophenes. Rice plants are mainly classified into three ecospecies, i. e., indica, japonica and javanica. Indica rice, which is mainly grown in South and Southeast Asia, can be classified into several ecotypes, such as aus, aman, boro, and tjereh, based on its morphological, physiological and ecological traits. Although ecotypic differentiation in japonica is less obvious than in indica, where the progressive improvement of rice cultivars has advanced further, it can be classified into two types, i.e., the northern and southern groups. The characteristics of javanica, which may consist of several ecotypes like Italian, Brazilian, bulu and so on, are also obscure to us.
Bulu, an ecotype of the javanica rice grown in the Southeast Asian archipelago, shows intermediate types between indica and japonica ecospecies in terms of physiological and ecological traits. Further analysis of the characteristics of the bulu ecotype is considered to be indispensable in order to establish a conceptual framework of the ecospecies and ecotypes of rice plants.
