| Chlorophyll synthetic gene(s) in T. aestivum
(var. Pb. C 591) Dalmir SINGH and B.C. JOSHI Division of Genetics, Indian Agricultural Research Institute, New Delhi, India A monosomic series was developed by Swaminathan et al. (1968) in a hexaploid strain of T. aestivum (var. Pb. C 591), with the help of monosomic series of Chinese spring developed by SEARS (1954). Both these monosomic series are being used in cytogenetical studies at the Indian Agricultural Research Institute, New Delhi. Utilizing these monosomic series, several genes have been located on specific chromosomes (SWAMINATHAN et al., 1968 ; SAWHNEY et al., 1978). In the present communication we report about chlorophyll synthetic gene(s) in T. aestivum var. Pb. C 591. Since the production of monosomic series, we have observed albina seedlings in monosomic. line 3A of Pb. C 591. Appearance of albina seedlings in the line mono 3A was presumed to be a spontaneous mutation which was being maintained in heterozygous condition. This assumption was based on the findings of NATARAJAN (1958) who for the first time found albina mutants in the M2 population of this variety. To confirm the spontaneous mutation theory, a number of monosomic plants were identified cytologically. Seeds of monosomic and disomic plants of line 3A were germinated separately and segregation was observed at seedling stage, since the albina seedlings can be easily identified. All the discomic plants produced only green seedlings. Monosomic plants on the other hand segregated for albina and green seedlings with a variable frequency of 9% to 15%. Expected monogenic ratio of albina : 3 green was not observed, which suggested that the segregation of albina plants in monosomic line 3A was not due to spontaneous mutation at this locus. To ascertain their somatic chromosome number, roots from different albina seedlings were analysed and it was found that all the albina seedlings had nullisomic (2n=40) chromosomal constitution. Somatic preparations of green seedlings showed that they had either 2n=41 (monosomics) or 2n=42 (disomics). Since albina seedlings are nullisomic (i.e. chlorophyll synthetic gene(s) bearing chromosomes are absent) for chromosome 3A, it can be suggested that chlorophyll synthetic gene or gene complex is located on chromosome 3A of T. aestivum var. Pb. C 591. |
| --> Next |