7. Identification of a null allele in traditional rice germplasm of Taiwan, China S.X. tang, G.S. kush and D.S. brar Division of Plant Breeding, Genetics and Biochemistry IRRI, P.O. Box 933, 1099 Manila, Philippines In isozyme analysis, those alleles that are not transcribed or that code for detective polypeptides lacking enzymatic activity are referred to as 'null alleles'. We analyzed 1604 genotypes of traditional rice germplasm from Taiwan, China, through starch gel electrophoresis for 16 isozyme loci following procedures of Glaszmann (1987). Null alleles were identified for 5 isozyme loci, namely Cat-1, Adh-l, Est-1, Est-2, Est-5 at a frequency of 0.25%, 0.12%, 4.93%, 54.61% and 0.19%, respectively. However, a null allele for Est-9, which was not reported earlier, was identified in 3 indica cultivars of Taiwan germplasm (Fig. 1).

54 Rice Genetics Newsletter Vol. 13

Est-9. located on chromosome 7 (Khush and Kinoshita 1991), has two alleles, Est-9^1 and Est-9^2 in proportion of 9.60% and 90.21%, respectively, in Taiwan rice germplasm. The null allele Est-9null was identified in three cultivars, namely Ti-Chueh-Chu-Tzu (Acc. 65424), Yun-Tzu-Ku (Ace. 65504) and Pao-Yeh-Chu (Ace. 78200). (Gene symbol: Old system)

References

Glaszmann,J.C., 1987. Isozymes and classification of Asian rice varieties. Theor Appl Genet 74: 31-20. Khush, G.S. and T. Kinoshita, 1991. Rice karyotype, marker genes and linkage groups. Pages 83-1089, In

Rice Biotechnology, G.S. Khush and G.H. Toenniessen, eds., CAB Intl., Oxford. U.K.