Rice Genetics Newsletter, Vol. 23

Rgn23

11.	*Mapping of the SWORD SHAPE DWARF1* gene, SSD1 in rice.**
	K. ASANO¹, M. ASHIKARI², A. MIYAO³, H. HIROCHIKA³, H. KITANO² and M. MATSUOKA² 1) Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601 Japan 2) Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi, 464-8601 Japan 3) Molecular Genetics Department, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8602 Japan

Use of dwarfism is one of the most available tasks for breeding program. Dwarfism arises from various types of defects, but two major factors responsible for dwarfism, gibberellin (GA) and brassinosteroid (BR), have been most intensively studied (Sakamoto et al. 2004, Hong et al. 2004). In contrast to the extensive characterization of dwarf mutants related to GA or BR, dwarf mutants with phenotypes that differ from the typical GA- or BR- related phenotypes have not been well characterized (Komorisono et al. 2005). Characterization of these mutants may be useful not only for breeding programs but also for understanding the mechanisms of stem elongation.

We identified a severe dwarf mutant, sword shape dwarf1 (ssd1), from Tos17 mutant lines (Hirochika 2001). Leaves of this mutant were sword shape-like (wide and short), rough and dark green. The seed fertility was low. These characteristics differ from those of the typical GA or BR-related mutants (Fig. 1). Genetic analysis indicated that the ssd1 mutation is recessive. We have not investigated linkage between this mutant and insertion of Tos17. We crossed ssd1 with indica cultivar Kasalath and used 13 F₂ plants with homozygous alleles of ssd1 for mapping. One sequence tagged site (STS) marker on the short arm of chromosome 3, S2188, was linked to the ssd1 mutation. Fine mapping using several molecular markers designed around this position revealed that the SSD1 is located within 2.2 cM genetic distance (Fig. 2). We are determining more precise location of SSD1.

References

Hirochika H., 2001. Contribution of the Tos17 retrotransposon to rice functional genomics. Curr. Opin. Plant Biol. 4: 118-122.

Hong Z., M. Ueguchi-Tanaka and M. Matsuoka, 2004. Brassinosteroids and rice architecture. J. Pestic. Sci. 29: 184-188.

Komorisono M., M. Ueguchi-Tanaka, I. Aichi, Y. Hasegawa, M. Ashikari, H. Kitano, M. Matsuoka and T. Sazuka, 2005. Analysis of the rice mutant dwarf and gladius leaf1. Aberrant Katanin-mediated microtuble organization causes up-regulation of gibberellin biosynthetic genes independently of gibberellin signaling. Plant Physiol. 138: 1982-1993.

Sakamoto T., K. Miura, H. Itoh, T. Tatumi, M. Ueguchi-Tanaka, K. Ishiyama, M. Kobayashi, GK. Agarawal, S. Takeda, K. Abe, A. Miyao, H. Hirochika, H. Kitano, M. Ashikari and M. Matsuoka, 2004. An overview of gibberellin metabolism enzyme genes and their related mutants in rice. Plant Physiol. 134: 1862-1653.