PNL Volume 21 1989 RESEARCH REPORTS                        61
EFFICIENCY OF SELECTION FOR MICROMUTATIONS IN M2 GENERATION IN PEAS
Singh, N.P. and B. Sharma                                                                  Division of Genetics
Indian Agric. Res. Institute, New Delhi, India
Comparative studies of selection in M2 and M3 generations have revealed that in many cases the two populations may not differ in response to selection (4,5). On the other hand, some experiments have demonstrated that selection in M3 is more effective than in M2 (1,2). This was, most probably, because the material already selected in M2 was confirmed with higher probability in subsequent generations (3). Even if the material selected in M3 or later generations has a higher probability of becoming fixed as promising strains, there is no evidence to suggest that the frequency of promising mutations per se is higher in M3 than in M2. It-can be argued that the variability manifested in M3 could not have arisen afresh without causing any impact on the M2 population. Therefore in the present study selection was initiated in the M2 generation on the basis of higher CV (variability) and desired shift in mean than the highest values in these parameters in the control (untreated population) for five polygenic traits (days to flowering, pods/plant, seeds/pod, 100-seed weight and yield/plant). The criterion for confirmation of the promising families in M3 was the shift in mean values in the desired direction. The selection efficiency in M2 generation, calculated on the basis of this criterion, is presented in Tables 1 and 2.
As can be seen from Table 2, 76.2-79.8% of M2 selections were confirmed as promising in the M3 generation. This suggests that selection in M2 was very effective and dependable. Some characters showed an increase in variance with the advance in generation to M3, which is confirmed by the fact that a further 22.2-24.8% of promising progenies were identified in M3. Nevertheless, early generation selection is of great help in reducing the volume of work, in saving time, and in isolation of confirmed mutations. As can be seen from Table 2, the contribution of the M2 and M3 generations to total selections arising from the different treatments was 75.2-77.8% and 22.2-24.8%, respectively. Thus, although new mutated progenies (about one-fourth of total) were added in the M3 generation (progenies which were either not identified in M2 or were new additions as a result of release of additional variability), the volume of material has to be increased very substantially in order to recover this smaller additional variability of a promising nature.
The overall analysis of the results obtained reveals that there is tremendous possibility to improve polygenic characters through induced mutagenesis by employing an efficient selection technique. It is evident that rigorous selection can help identify promising variants from the mutagenized populations in the first segregating (M2) generation. These variants can simultaneously be confirmed and their potential tested in the M3 generation.
1.   Jana, M.K. and K. Roy. 1973. Radiation Bot. 13:245-257.
2.    Palezona, D.L. 1966. Proc. V. Yugoslav Symp. on Research in Wheat 12:255-261.
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PNL Volume 21 1989 RESEARCH REPORTS
3.    Ravi, J.L. and Manocha and Avtar Singh. 1979. Proc. BARC Symp. on Role of Induced Mutations in Crop Improvement, Hyderabad, pp. 414-419.
4.   Scossiroli, R.E. 1968. Mutations in Plant Breeding II. IAEA, Vienna, pp. 205-217.
5.   Sharma,S.K. 1977. Ph.D. Thesis, IARI, New Delhi.
Table 1. Selection efficiency for micromutations in M2 and M3 generations (pooled over five traits).
Mutagen
M2 generation
M3 generation
Total progenies
Promising selections (%
Total progenies )
Promising selections (%)
Gamma rays
1200
16.6
786
30.3
EI
1200
21.2
786
35.9
NEU
1200
24.5
842
38.4
Table 2. Nature of M2 selections and their contribution to total micromutations (pooled over five traits).
Mutagen
M2 selections
Proportion of total selections (%)
Total
Confirmed in M3 (%)
M2 selections
M3 selections
Gamma rays
189
76.2
76.2
23.8
EI
230
77.5
77.8
22.2
NEU
274
79.9
75.2
24.8
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