27. Geographical distribution of esterase genotypes of rice in Asia


Masahiro NAKAGAHRA

National Institute of Aerobiological Resources, Tsukuba, 305 Japan


Esterase variations of Asian rice cultivars are determined by genes at 4 loci, Est-1, Est-2, Est-3 (Nakagahra 1977), and Est-4 (Unpublished). Alleles so far found are 2 at Est-1 (Est-1 and Est-1nul), 3 at Est-2 (Est-2S, Est-2F, and Est-2nul) , 2 at Est-3 (Est-3S and Est-3F), and 3 at Est-4 (Est-4S, Est-4F, and Est-4nul). Est-2 is located on Chromosome 7 (1st Linkage group) with the following gene sequence and linkage intensities (Nakagahra and Hayashi 1976).






There was no evidence for linkage between Est-1 and Est-2 or between Est-2 and Est-3 (Nakagahra 1977). The geographical distribution of genotypes for these enzymes was reported earlier with 1,190 indigenous rice cultivars (Nakagahra 1978). Since then, the present author and coworkers have explored different regions of Asia to obtain more material, and have studied a total of 2,752 native varieties.


With regard to the Est-1, Est-2, and Est-3 loci, 12 genotypes were found as follows:


    Est-1   Est-2   Est-3          Est-I     Est-2     Est-3
1       1   2S      3F         7     nul       2S        3F
2       1   2S      3S         8     nul       2S        3S
3       1   2F      3F         9     nul       2F        3F
4       1   2F      3S        10     nul       2F        3S
5       1   nul     3F        11     nul       nul       3F
6       1   nul     3S        12     nul       nul       3S

The frequencies of these genotypes in 13 regions of Asia are shown in Fig. 1. North China (NC) and Japan (JP) were dominated by genotype 6, India-Sri Lanka (IN), Nepal (NE) and Bhutan-Northeastern India (AS) by genotype 1, and Vietnam (VT), South China (SC) and Malaysia (ML) by genotype 3. The frequencies of genotypes 1, 3 and 6 showed geographic clines clearly. Diversity was highest in the area covering Burma (BU), Thailand (TH), Laos (LA), and Yunnan Province of China. This area may be regarded as a diversity center for rice.


Fig. 1. Geographic distribution of esterase genotypes in native reice varieties in Asia.





References

Nakagahra, M. and K. Hayashi 1976. Detection of esterase isozyme loci of Oryza sativa L. Jpn. J. Breed 26 Suppl. 1: 114-115 (in Japanese).

-----, 1977. Genic analysis for esterase isoenzymes in rice cultivars. Jpn. J. Breed. 27: 141-148.

-----, 1978. The differentiation, classification and center of genetic diversity of cultivated rice by isozyme analysis. Trop. Agric. Res. Ser. 11: 77-82.