RICE GENETIC-RESOURCES - HISTORY, CONSERVATION, INVESTIGATIVE CHARACTERIZATION AND USE IN JAPAN

Rice has been grown in Japan for about 3000 years. Although both japon ica and indica varieties have been grown in Japan, now japonica rices are grown. Japanese rice breeding has used an ecological breeding appr oach. While emphasis in rice breeding in the 1940's and 1950's focusse d on yield in recent decades quality has been of major importance. Con sumer preference and name recognition of high quality varieties, such as Koshihikari, has resulted in slow acceptance of new varieties. Rice germplasm was systematically collected throughout Japan between 1962 and 1963. Subsequent acquisition and collecting, in Japan and other co untries, has resulted in 28,000 accessions being conserved in the Nati onal Genebank, based at the National institute of Agrobiological Resou rces (NIAR). Research on genetic diversity of rice using a range of te chniques, for example esterase isozymes, has revealed clinal variation in rice radiating from the center of diversity of rice in and around southwest China. Newly found genes in traditional rice germplasm, such as genes for non-elongating mesocotyl, are now routinely identified o n the rice genome. Pioneering studies on eco-genetic differentiation o f species in the genus Oryza in Japan has revealed much about the comp lex genepool for which rice evolved. Pest and disease resistance sourc es, particularly to blast, bacterial blight and brown plant hopper, fr om many countries have been incorporated into Japanese varieties. Cold tolerance at the booting stage was found in the Indonesian variety Si lewah. In the future in characterisation of rice germplasm and interac tion between rice germplasm specialists and rice molecular scientists, both in Japan and internationally, will be corner stones to securing rice genetic diversity and rice improvement in the next century.