Atomic Energy Laboratory, I.A.R.I., New Delhi-12
**Present address: Department of Plant Breeding & Genetics, College of Agriculture, OUAT, Bhubaneswar-3.
*Part of the thesis submitted by the first author to the Post-Graduate School, I.A.R.I., New Delhi in partial fulfilment of the requirements for the Ph.D. degree.
To study the mode of inheritance of the speltoid supressor gene Q , in wheat, ten chemically induced homospeltoid mutants of the variety, ‘Sonora 63’, were crossed among themselves and with the parent. From the pattern of segregation in F2 of different crosses, it is inferred that different strengths of Q , occur in different homospeltoid parents. The homospeltoid phenotype could be expressed either after a deletion or functional alteration of the Q , genes in one homologue. This may be a speciality of the action of EMS on gene repeats. The plants exhibit homospeltoid phenotype upto three doses of Q , including both the homologues of 5A chromosome. Four to five doses of Q , are exhibited as heterospeltoid phenotype and with six doses of Q , the phenotype becomes free threshing. There were evidences from this investigation that spcltoids, after a certain threshold of Q , dosage, tend towards the phenotype of vulgare types.
Contrary to the previous finding of differential transmission of gametes in homospeltoids, the present findings reveal that the induced alterations are transmitted through both the gametes and behave in a similar way as the spontaneously occurring genotypes for these phenotypes.
