11. Mapping of the lazy gene, la

1) Bioscience and Biotechnology Center, Nagoya University, Nagoya, 464-8601 Japan
2) Institute of Botany, Academia Sinica, Taipei, 11529 Taiwan

The cereal plants grow up forward on the ground. The rice lazy(la) mutant was characterized as a spreading or prostrate growth by an inability to respond or reduced responsiveness to gravity (Fig. 1. Jones and Adair, 1938; Abe and Suge, 1993). This characteristic was also identified in other cereals such as maize (Overbeek, 1936) and barely (Suge and Turkan, 1991). The rice la gene was assigned to the long arm of chromosome 11by the linkage analysis using telotrisomics (Singh et al., 1996), and was mapped at 13.1 cM from XNpb202 (Kishimoto et al., 1993) or 28.8 cM from RG118 (Yu et al., 1995). Abenes et al. (1994) also mapped la to be near the middle of chromosome 11 and in between RG1094 and RG247. On the other hand, Wu et al. (2002) estimated the distance between la and RG247 to be 16 cM instead of 6.2 cM, which was previously reported by Abenes et al. (1994), and therefore the precise map position of la has not been clarified yet.

In order to map the la locus, we crossed the la mutant of japonica rice cv. Taichung 65 with an indica rice cv. Kasalath containing the wild-type allele (La/La). The F1 plants were then cultivated and self-pollinated to obtain F2 seeds. In the F2 seedlings, we screened homozygous seedlings for la by the agravitropism habit and isolated the genomic DNAs for the linkage analysis. We collected about 2,300 F2 la homozygous plants, and investigated the linkage between the la locus and three molecular markers, R728, C459B and T57, located near the La locus. Linkage analysis revealed that La was located between R728 and C459B, with distance of 1.0 cM and 0.4 cM, respectively (Fig. 2). We are now performing fine map analysis of La using several new markers located between R728 and C459B to isolate and character-

ize the La gene.


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