Genomic selection is attracting attention in the field of crop breeding. To apply genomic selection effectively for autogamous (self-pollinating) crops, an efficient outcross system is desired. Since dominant male sterility is a powerful tool for easy and successive outcross of autogamous crops, we developed transgenic dominant male sterile rice (Oryza sativa L.) using the barnase gene that is expressed by the tapetum-specific promoter BoA9. Barnase-induced male sterile rice No. 10 (BMS10) was selected for its stable male sterility and normal growth characteristics. The BMS10 flowering habits, including heading date, flowering date, and daily flowering time of BMS10 tended to be delayed compared to wild type. When BMS10 and wild type were placed side-by-side and crossed under an open-pollinating condition, the seed-setting rate was <1.5%. When the clipping method was used to avoid the influence of late flowering habits, the seed-setting rate of BMS10 increased to a maximum of 86.4%. Although flowering synchronicity should be improved to increase the seed-setting rate, our results showed that this system can produce stable transgenic male sterility with normal female fertility in rice. The transgenic male sterile rice would promote a genomic selection-based breeding system in rice.

The genus Rosa contains more than 150 species that are widely distributed throughout the Northern Hemisphere. Their basic chromosome number is seven, and their ploidy levels range from diploid to octoploid species. Hurst (1925, 1928) considered the basic chromosome number "septet" as a unit, and he classified diploid rose species into five categories, septets A to E, based on the morphological, physiological and ecological characteristics, mitotic and meiotic chromosome configurations and genetical tests. Polyploid species have more than two identical or different septets. Modern cultivated roses were developed through crosses among only eight diploid species, which are all classified into septet A (Wylie 1954).Chromosomal information is an important key for the classification, phylogenetic analysis and evolutionary biology of plant species, as well as for their morphological and physiological characteristics. Until recently, components of metaphase chromosomes, i.e., number, length and arm ratio, had been commonly used to identify the karyotype of a species, except for maize and rice pachytene chromosomes. Especially in the case of horticultural plants, whose metaphase chromosomes are relatively small compared to those of other plant species, it had been difficult to discriminate individual chromosomes. However, since Fukui and Mukai (1988) developed a method for analyzing prometaphase chromosomes, ideograms of many plant species with small chromosomes have been constructed (for review, see Fukui et al. 2000).In order to clarify the phylogenetic relationships among the wild rose species, we attempted to compare the karyotypes and the physical location of the genes with repetitive sequences. Since the chromosomes of wild roses are small at the mitotic metaphase stage, it was difficult to discriminate each of the chromosomes. However, in our previous studies (Akasaka et al. 2002), ideograms were successfully constructed for five wild rose species by observing the prometaphase chromosomes, and rRNA genes were located on the ideograms. In the present paper, the characteristics of the karyotypes of four wild rose species belonging to septets B, C, and D are described.The four wild rose species used in this study are listed in Table 1. All the plant materials were grown from cut seedlings in pots in a greenhouse located at the Faculty of Horticulture, Chiba University, Japan. Root tips were collected from the seedlings showing vigorous growth, treated with distilled water at 4°C for 16-17 h and fixed in Farmer's fluid (ethanol : acetic acid = 3 : 1) at 4°C for at least 2 days. After treatment with an enzyme mixture consisting of 3 %(w/v) Cellulase Onozuka RS, Yakult, 1.5 %(w/v) Pectolyase Y-23, Seishin, in 0.01 M sodium citrate, pH 4.6 at 37°C for 50-60 min, the root tips were placed on glass slides and exposed to steam over hot water at 76°C for 2 sec. Then, they were tapped with a forceps in a few drops of the fixative (methanol : acetic acid = 3 : 1), re-exposed to steam and air-dried on a hot plate at 60°C for 2...

In order to clarify the origin of weedy rice (Oryza sativa L.) in Okayama Prefecture, Japan, we used a set of 15 sequence-tagged site primers to analyze polymorphisms among 27 weedy rice accessions and 88 cultivated rice varieties accessions including common rice varieties from Okayama. The band patterns indicated that 13 of the japonica weedy accessions corresponded exactly with one of the japonica cultivated rice varieties. Furthermore, with the exception of a strong shattering habit, these japonica weedy accessions closely resembled each corresponding rice variety in morphophysiological characteristics. Consequently, in view of the close genetic homology and high morphophysiological resemblance between weedy rice and cultivated rice varieties in Okayama, we conclude that weedy rice originated from cultivated rice varieties as an "offtype" caused by genetic mutation accompanied by the development of a strong shattering habit.

We aimed to elucidate the molecular nature of the seed-shattering habit of weedy rice Oryza sativa L. in Okayama Prefecture, Japan, which seems to be an "off-type" of the main rice varieties in Okayama. We performed time-course analyses of breaking tensile strength (BTS) and analyzed the histological features of pedicels; we also genotyped the seed-shattering genes qSH1 and sh4 of weedy rice accessions and rice cultivars. The BTS of weedy accessions and cultivars began to decrease simultaneously at three weeks after heading. The weedy accessions showed complete loss of BTS and grain dispersal at five weeks after heading. In contrast, the cultivars maintained a certain degree of BTS and did not exhibit grain dispersal. Pedicel structures, which affect BTS, differed between the weedy accessions and the cultivars. The weedy accessions had complete and cracked abscission layers, while the cultivars had incomplete and uncracked abscission layers; however, the qSH1 and sh4 sequences that influence the formation of the abscission layer showed no differences between the weedy accessions and cultivars. We surmise that the shattering habit of weedy rice in Okayama is caused by formation and degeneration of the abscission layer, mediated by unidentified shatteringrelated gene(s).