Abstract
A new method was developed for preparation of highmolecularweight (HMW) DNA from rice using young or mature leaves as source material. Compared with the ori-ginal method, in which germ' tissues were used as source material (Hatano et al., 1992), the new method is simpler and faster because the procedure for isolation of germ tissues is no longer necessary. Moreover, even if a limited supply of seeds is expected, HMW DNA can be prepared from mature leaves derived from a smaller number of seeds. Therefore, the method is suitable for screening genomes of a number of varieties of rice for analysis by pulsedfield gel electrophoresis. HMW DNA from rice varieties that included nine Japonica cultivars, one Indica cultivar, and one strain of Oryza puuctata, a wild rice was prepared by the newly developed method. Each of the samples was digested with restriction enzymes and fragments were separated by pulsedfield gel electrophoresis. After staining of gels, a microfine banding pattern was visualized over a smeared background in each lane. Each pattern was specific for a specific variety of rice. Furthermore, although similarities were found among the Japonica cultivars tested, few common microbands were observed among the Indica cultivar, the strain of Oryza punctata and the group of Japonica cultivars tested. These observa-tions indicate that a high degree of polymorphism of nuc-lear DNA among rice varieties can be detected by simple staining of gels after pulsed-field gel electrophoresis.
