Improvement of Tongil-Type Rice Cultivars from Indica/Japonica Hybridization in Korea

Abstract

The most crucial factor for the crop improvements lies in the possibility of hybridization between the various genetic sources and thus more diversified genetic resources are needed. Rice has been widely cultivated under diverse climatic, hydrological, and edaphic conditions. Among rice cultivars, indica cultivars, which are usually grown in tropical areas, have more diverse genetic resources than japonica cultivars due to diverse habitats. Japonica cultivars, on the other hand, are grown mainly in temperate areas such as Korea, Japan, and northern China, and thus exhibit relatively narrow genetic diversity. Introduction of indica’s desirable characters to japonica was not commonly done, due to the high incidence of spikelet sterility and the incorporation of undesired characters in the progeny. Indica cultivars were used only for special purposes such as breeding for resistance to specific diseases and insects in the indica/ japonica hybridization.