Polymorphism for a-amylase genes in barley

Tetsuo Takano*, Genkichi Takeda and
Chikako Kiribuchi
Laboratory of Plant Breeding
Faculty of Agriculture
The University of Tokyo
Yayoi, Bunkyo-ku, Tokyo 113, Japan
*Present address: Experimental Farm, Faculty of Agriculture, The University of Tokyo, Tanashi, Tokyo 188, Japan.

We have examined the genetic variations of a-amylase synthesized during germination using barley varieties (Takano and Takeda, 1985, 1987, 1988; Kiribuchi and Takeda, 1988). When a-amylase isozymes are separated by isoelectric-focusing (IEF), they are divided into low and high pI groups which are controlled by the genes located on chromosome I and 6, respectively (Brown and Jacobsen, 1982; Muthukrishnan et al., 1984). We classified the varieties into three isozyme types (type 1, 2, and 3) based on the banding patterns of high pI groups (Fig. 1, Takano and Takeda, 1985). We also analyzed the F2 and F3 segregation for the banding patterns of a-amylase isozymes. The results indicated that the three types had co-dominant relationships basically, but the new banding patterns were obtained with a low frequency. In the F4 generation, we obtained several lines with these new banding patterns (Fig. 1, Takano et al., 1988; Kiribuchi and Takeda, 1988). Since cz-amylase in barley is controlled by multigene families (Muthukrishnan et al., 1983; Rogers and Milliman, 1984), we preliminarily estimated that these new banding patterns were obtained as a result of the genetic recombinations between the multigene families (Takano et al., 1988). We felt that the gene coding for band 10 was newly detected because this band was specific to the type 1 varieties which were found only in the varieties bred in Japan (Takano and Takeda, 1985), and that this gene is linked with the other genes. The recombination value estimated was 5.3 to 9.7% (Takano et al., 1988).

Based on the results mentioned above, we investigated the polymorphism for the ce-amylase genes by restriction fragment length polymorphisms (RFLPs) method using high pI a-amylase cDNA (Rogers, 1985) as a probe. Analyzing 9 varieties which belonged to three IEF types and 11 bred lines which exhibited homozygous new IEF banding patterns, we detected three RFLPs patterns (type A, B, and C) which means there are three types of structural genes (Fig. 2). All the type 1 varieties by IEF showed type A pattern, all the type 3 varieties by IEF showed type C pattern and the type 2 vareieties by IEF showed type B or C pattern. As to the bred lines from the cross between Clipper (type 2,B) and Haruna Nijo (type 1,A), all the lines of type 2 + band 10 showed type A pattern and all the lines of type 1 - band 10 showed the type B pattern. From this result, we assume that a regulatory gene affects the banding patterns of IEF. With this assumption, the new banding pattern is thought to be produced by the genetic recombination, not between the new gene coding for band 10 and the other structural genes, but between the structural genes and the regulatory gene (Kiribuchi et al., 1989).

Fig.l.Banding patterns (bands 10-16) detected by isoelectric-focusing.

Fig.2. RFLP Patterns detected by a high pI a-amylase cDNA probe. 10microgram of barley DNA were digested with Hind III.


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