I. Research Notes

Induced M₁ sterility and mutation frequency in Triticum aestivum

M. P. SINGH, S. D. DUBEY and N. C. SINGHAL

Division of Genetics, Indian Agricultural Research Institute, New Delhi- 12, India

It is now known that M₁ spikes after mutagenic treatments exhibit a range of variation in the degree of sterility. Earlier reports on the effects of M₁ seed fertility on mutation frequency in M₂ (GAUL 1958, 1964, EHRENBERG et al. 1961, KIVI 1965, SHARMA and BANSAL 1970) are not consistent. These observations were based on chlorophyll mutation frequency in genus Hordeum vulgare. For our present studies, different varieties of bread wheat (Triticum aestivum) were used as a test material. The observations were recorded on viable phenotypically detectable mutants. The mutation frequency was calculated on total M₂ population scored. Induced M₁ sterility has been used as an indicator parameter. The results pertaining to fertility and mutation percentage in different sets of treatments and varieties are summarized in Table 1.

The data compiled in Table 1 is taken from different sets of experiments representing the observations of ten different years. From the results an obvious conclusion can be drawn that irrespective of the treatments, dosage effects, varietal response or genotype treatment interaction, the reduced fertility in M₁ generally gives higher mutation frequency in M₂. The cytological studies have indicated that induced cryptic and gross chromosomal changes in M₁ are mainly responsible for the re-patterning of the genetic material and thereby affecting the seed fertility level. GAUL (1961) suggested that the sterility in M₁ spikes, in term of seed setting should serve as an indication of the frequency of chromosome mutations.

If the aim is to maximise the viable mutation rate, then it would be better to restrict to a few effective treatments, which will have limited M₂ population. With the increased sterility the mutation frequency was considerably enhanced, but there was no change in the mutation spectrum. These results should be of interest having practical implications for planning mutation breeding programmes. The fertility range of 50% or less can be used as a reliable indicator parameter for selecting the most potent genotype treatment combination.

Literature cited

EHRENBERG, L., A. GUSTAFSSON and U. LUNDQUIST 1961. Hereditas 47: 243-282.

GAUL, H. 1958. Z. F. Pflanzenzucht 40: 151-188.

GAUL, H. 1961. Effects of ionizing radiations on seeds. I.A.E.A., Vienna.

GAUL, H. 1964. Radiation Botany 44: 155-232.

KIVI, E. I. 1965. The use of induced mutation in plant breeding. FAO/IAEA, Vienna.

SHARMA, R. P. and H. C. BANSAL 1970. Indian J. Genet. 30: 544-550.

(Received May 22, 1972)