ALIGNMENT OF MOLECULAR AND CLASSICAL LINKAGE MAPS OF RICE, ORYZA-SATIVA

Application of genetic linkage maps in plant genetics and breeding can be greatly facilitated by integrating the available classical and mol ecular genetic linkage maps. In rice, Oryza sativa L., the classical l inkage map includes about 300 genes which correspond to various import ant morphological, physiological, biochemical and agronomic characteri stics. The molecular maps consist of more than 500 DNA markers which c over most of the genome within relatively short intervals. Little effo rt has been made to integrate these two genetic maps. In this paper we report preliminary results of an ongoing research project aimed at th e complete integration and alignment of the two linkage maps of rice. Six different F2 populations segregating for various phenotypic and RF LP markers were used and a total of 12 morphological and physiological markers (Table 1) were mapped onto our recently constructed molecular map. Six linkage groups (i.e., chr. 1, 3, 7, 9, 11 and 12) on our RFL P map were aligned with the corresponding linkage groups on the classi cal map, and the previous alignment for chromosome 6 was further confi rmed by RFLP mapping of an additional physiological marker on this chr omosome. Results from this study, combined with our previous results, indicate that, for most chromosomes in rice, the RFLP map encompasses the classical map. The usefulness of an integrated genetic linkage map for rice genetics and breeding is discussed.