Beijing Agriculture University, Ma-Lian-Wa, Beijing, 100094 China
Four esterase gene loci, Est-10, Est-11, Est-12 and Est-13, were newly identified after polyacrylamide gel electrophoresis with a large number of O. sativa landraces and O. rufipogon wild strains of Asian origin. The bands expressed by the four loci can be distinguished from one another by certain characteristics as shown in Table 1.
Est-10(t) expresses a single band which is monomer. It has one recessive (1) and four codominant (2, 3, 4 and 5) alleles whose bands differ in mobility, and a
Table 1. Characteristics of esterase bands controlled by four new loci
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Locus organ Migration Color Band, double Monomer Chromosome
exhibiting rate or single or dimer located
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Est-10 Seed Slow Brown Single Monomer 1
Est-11 Seed Fast Double Dimer -
Est-12 Seedling* Very fast Single Monomer 9
Est-13 Seedling* Very slow Double Monomer 5
Est-2 Seed & In-between Red Single Monomer 6
Seedling Est-10&-11
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*Plumules of seedlings.
null allele (recessive). F`2` segregation patterns were observed in 29 crosses involving the four active and one null alleles. The first (Est-101), second (Est- 102 ) and third (Est-103) alleles show a high frequency of distribution in Japonica, Indica and aus varieties, respectively. The fourth (Est-104) allele was frequent in long-duration cultivars such as aman and rayada and in O. rufipogon. The fifth allele (Est-105) was rare and found only in a few Chinese O. rufipogon strains. The null allele was frequent in aus and bulu varieties.
In a doubled haploid series raised from an Indica-Japonica cross (ZYQ8 X JX17), the linkage of Est-10 with RFLP markers was examined. It was found that Est-10 was linked with RG220 located on chromosome 1 (Fig. 1a). Another cross also showed the linkage of Est-10 with Est-5 which is located on chromosome 1. No other esterase loci than Est-5 have so far been found on this chromosome. This confirms that Est-10 differs from the nine esterase loci so far identified (by starch gel electrophoresis; Morishima and Glaszmann 1990).
Est-11(t) confers a double band which is dimer. The band migrate faster than Est-2 but slower than Est-12. Three codominant alleles (1, 2 and 3) and a null allele have so far been found. Allele 1 is distributed in both Indica and Japonica cultivars in common. Allele 2 was found in an O. rufipogon strain from China, and allele 3 in O. barthii (=breviligulata). The null allele was found in boro varieties from India. The linkage relation of Est-11(t) remains unknown. Its dimer production makes it unique.
Est-12(t) produces a single band (monomer) which migrates faster than Est-11(t). An active allele was found in Indica cultivars, and a null allele in Japonica cultivars. Segregation patterns were observed in an F`2` (Acc.13OX Acc.221), and in a doubled haploid series raised from an Indica-Japonica cross (ZYZ8 X JX17) which showed a 1 active: 1 null ratio. The linkage with RFLP markers was examined, which showed that Est-12 was linked with RZ12 and located on chromosome 9 (Fig. 1b). On this chromosome, Est-3 is known to be located (Nakagahra 1977), but it has a slow and a fast band and differs from Est-12 (t) apparently.
Est-13(t) produces a double band which is monomer. it migrates slower than Est-10. Two active alleles, 1 and 2, are found. Alleles 1 and 2 are common in Indica and Japonica cultivars, respectively. An investigation of the linkage with RFLP markers showed that Est-13(t) was linked with RG13 and RG474 which are located on chromosome 5 (Fig. 1c). No esterase gene has so far been found on chromosome 5.
References
Morishima, H. and J. C. Glaszmann, 1990. Current status of isozyme gene symbols. RGN 7: 50-57.
Nakagahra, M., 1977. Genic analysis for esterase isozyme in rice cultivars. Japan. J. Breed. 27: 141-148.