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D. Research
Notes1. Varietal Differentiation
S.S. malik and G.S. khush
International Rice Research Institute, P.O. Box 933, Manila, Philippines
The cultivated rice (Oryza sativa) shows remarkable variation which has been of great interest to rice breeders and geneticists. Several workers (Kato et al. 1928) based on the morphological and serological characters as well as intervarietal fertility have classified 0.sativa into two main types Japonica and Indica. Similarly Chinese scientists classified rice varieties into two types: Hsien (Indica) and Keng (Japonica). On the basis of morphological characters and geographical distribution Matsuo (1952) classified cultivated rice into three types: japonica, javanica and indica. However, Oka (1958) considered both japonica and javanica morphological types as temperate and tropical components of a japonica group, respectively.
Isozymes such as peroxidase (Pai et al. 1973), acid phosphatase (Pai et al.1975), esterases, (Nakaghara 1977) provide valuable tools to classify the rice germplasm into varietal groups. Glaszmann (1986) identified 6 groups among 120 Asian rice varieties based on 5 isozyme loci, e.g., Pgi-1, Pgi-2, Amp-l, Amp-2 and Amp-3. Among the 6 groups two major groups were identified: group I consisting of typical indica varieties and group VI composed of temperate and tropical japonica rices. The other groups, e.g., II, III, IV and V share common differences from groups I and VI .
We have analyzed 6532 traditional rice varieties of Philippines and Thailand for 16 isozyme loci. Based on the 5 loci (Pgi-1, Pgi-2, Amp-3, Amp-2 and Amp-l) suggested
Table 1. Distribution of Cat-1 alleles in rice germplasm
|
Varietal |
Group |
||||||
|
Country |
Cat-1 |
l(lndica) |
VI(Japonica) |
Total |
|||
|
Allele |
No. |
(%) |
No. |
(%) |
No. |
(%) |
|
Philippines |
1 |
590 |
99.15 |
37 |
3.65 |
627 |
39.1 |
|
2 |
5 |
0.84 |
973 |
96.05 |
978 |
60.9 |
|
Thailand |
1 |
4058 |
99.87 |
2 |
1.02 |
4060 |
82.9 |
|
2 |
2 |
0.03 |
834 |
98.97 |
836 |
17.1 |
|
1 |
1 |
4648 |
99.84 |
39 |
2.11 |
4687 |
72.1 |
|
2 |
7 |
0.15 |
1807 |
97.88 |
1814 |
27.9 |
|
Research Notes
by Glaszmann (1987) we found 4655 (71.2%) to belong to group 1, 1849 (28.3%) to group VI and 28 (<0.5%) in other groups including intermediate group (Table 1). Our analysis showed that as many as 99.9% of the varieties in group I had allele I of Cat-1. On the other hand 97.88% of the group VI varieties showed allele 2 of Cat-1. These findings suggests that germplasm can be classified into groups I and VI based on allelic composition at a single isozyme locus (Cat-1) in more than 97% of the cases. Such simple procedure can save the time and resources to discriminate the rice germplasm into two groups. (Gene symbol: Old system)
References
Glaszmann, J.C., 1986. A varietal classification of Asian cultivated rice (Oryza sativa L.) based on isozyme polymorphism. Pages 83-90 In Rice Genetics. International Rice Research Institute, P.O. Box 933, Manila, Philippines.
Glaszmann.J.C., 1987. Isozymes and classification of Asian rice varieties. Theor Appl Genet 74:21-30.
Kato, S., H. Kosaka and S. Hara, 1928. On the affinity of rice varieties as shown by fertility of hybrid
plants. Bull. Sci. Fac. Agric., Kyushu Univ., Fukuoka, Japan 3: 132-147.
Matsuo, T., 1952. Genecological studies on cultivated rice. Bull. Natl. Inst. Agri. Sci. Jpn. D3: 1-11.
Nakagahra, M. 1977. Genetic analysis for esterase isozymes in rice cultivars. Jpn. J. Breed. 27: 141-148.
Oka. H.I., 1958. Intervarietal variation and classification of cultivated rice. Ind. J. Genet. Plant Breed. 18:
79-89.
Pai, C., T. Endo and H.I. Oka, 1973. Genie analysis for peroxidase isozymes and their organ specificity in
Oryza perennis, and 0. sativa. Can. J. Genet. Cytol. 15: 845-853.
Pai, C., T. Endo and H.I. Oka, 1975. Genie analysis for acid phosphatase in Oryza perennis and 0. sativa.
Can. J. Genet. Cytol. 17: 637-650.
