Fig. 1. Diagrammatic representation of zymograms of Mal isozymes.
Department of Agronomy, Beijing Agricultural University Ma Lian Wa, Beijing, 100094 China
A total of 176 rice varieties (Oryza sativa L.) from China and 16 other countries were studied. Seeds were examined in 137 varieties, plumules of growing plants in 60, and both seeds and plumules in 21 varieties. The PAGE (polyacrylamide gel electrophoresis) tris-citric acid system was employed, and the staining method followed Glaszmann et al. (1988).
The loci dealt with in this paper are Mal-1, Mal-2, Mal-3 and Mal-4. Mal implies malate dehydrogenase similar to Mdh. Mal differs from Mdh in that it needs NADP as coenzyme in the substrate, while Mdh needs NAD. At Mdh-1, two alleles (1 and 2) were found in Oryza rufipogon, but no variation was found in cultivars (Morishima and Glaszmann 1990). At Mal-1, two alleles (1 and 2) were found, which were frequent in the Japonica and indica varietal groups, respectively (Morishima and Glaszmann 1990). The zymograms of these isozymes are diagrammatically depicted in Fig. 1.
Mal-1 and Mal-2 were found in the plumules of growing plants. Mal-1 is located on chromosome 1, and Mal-2 is on chromosome 7 according to Zhu et al. (1993). Each locus had two alleles, 1 and 2. Most Japonica varieties had Mal-11 and Mal-22 while most Indicas had Mal-12 and Mal-21 (Table 1). The Aus varieties, although they belong to the Indica group, mostly showed Mal-22 which is frequent in the Japonica group.
Mal-3 and Mal-4 were found in sprouting seeds. Mal-4 possessed four
Fig. 1. Diagrammatic representation of zymograms of Mal isozymes.
Table 1. Distribution of alleles of Mal-1 and Mal-2 among rice varieties
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Varietal group No. of Mal-1 Mal-2
varieties Allele: 1 2 1 2
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Indica 18 0 18 14 4
Indica, Aus 9 1 8 2 7
Japonica 33 29 4 8 25
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Table 2. Distribution of alleles of Mal-3 and Mal-4 among rice varieties
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No. of Mal-4 Mal-3
Varietal group varieties Allele: 0 1 2 3 1 2
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Indica 52 6 28 6 12 28 24
Indica, Aus 28 1 4 2 21 4 24
Japonica 57 2 0 53 2 0 57
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alleles, null (0), 1, 2 and 3 (Fig. 1). Most Japonicas has Mal-4 , while
most Indicas had either Mal-4`1` or Mal-4`3` (Table 2). At Mal-3, two alleles
were found. Mal-31 was frequent in the Indica group and tended to associate
with Mal-41. All Japonica verieties examined had Mal-3 . Many of Aus
varities showed the Japonica allele, Mal-32 . They seem to share some genes
with Japonica varieties.An F`2` population of 95 plants from Sui 619xNanjing 11 segregated into 22 plants with Mal-31, 44 with Mal-31/2 and 29 with Mal-32, fitting a 1: 2: 1 ratio and confirming the allelism of Mal-31 and Mal-32. In addition, a doubled haploid population from JX17 x ZYQ8 were observed (Table 3). The population consisted of two homozygous parental types. The F`2` population from TKM9 x Akihikari proved the allelism of Mal-11 and Mal12, as well as of Mal-21 and Mal-22(Table 3).
Table 3. Segregation patterns observed for Mal-1 and Mal-2 alleles
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Generation Cross No. of Geno- Mal-1 Mal-2
plants type: 11 12 22 11 12 22
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Doubled JX17xZYQ8 60 41 0 19 30 0 30
haploid
F`2` TKM9xAkihikari 106 28 38 40 40 42 24
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ReferencesGlaszmann, J. C., B. G. de los Reyes and G. S. Khush, 1988. Electrophoretic variation of isozymes in plumules of rice - A key to the identification of 76 alleles at 24 loci. IRRI Res. Paper Ser. 134: 1-14.
Morishima, H. and J. C. Glaszmann, 1990. Current status of isozyme gene symbols. RGN 7: 50-57.
Zhu, Li-Huang, Ying Chen, Yuu-Bin Xu, Ji-Chen Xu, Hong-Wei Cai and Zhong-Zhuan Ling, 1993. Construction of a molecular map of rice and gene mapping using a double haploid population of a cross between Indica and Japonica varieties. RGN 10: 132-135.