| Results and Discussion Progeny means and analysis of variance There were highly significant differences among progenies for days to 50 per cent flowering (Table 1). All the three components of this variation viz: pure cultures, mixtures and pure cultures vs mixture showed highly significant variation. The range of variability among pure cultivars was from 107 to 122 days whereas the mixture showed a range from 108 to 120 days. This indicated that the variation in mixtures as a group was less as compared to that in case of pure cultivars which is apparent from the proportion of mean squares also. The variation in flowering period is useful in the sense that multilines with varying maturity period could be developed to fit in various crop sequences. In the multiline breeding programme being pursued at the Punjab Agricultural University an effort has been made to develop multilines with different flowering period. As in case of flowering period, for plant height also there were significant differences among pure cultures as well as among mixtures. The contrast between the two groups was also highly significant. The range of variability for pure cultures was from 90.1 cm (for ML-328) to 103.3 cm (for ML-319). The corresponding range for mixture was from 93.5 cm (ML-246+ML-419) to 103.7 cm (ML-267+ML-378). It may be observed that the variability in mixture is less than that in pure standards. It may be noted that in a mixture whenever a late flowering parent (ML-323 or ML-328) was used it resulted in delay in flowering. As far maturity period, efforts at this University have been made to develop multilines in Kalyansona cultivar with varying height also so that multilines of different height could be released for different fertility levels. The indicated height differences in pure-cultures are being exploited in this direction. It would be worthwhile to make two types of comparisons. First what is the performance of the mixture when two phenotypically divergent genotypes are mixed. The second would be the comparison of the performance of the mixture when the two phenotypically similar (almost same height) parents are grown in a mixture. In the present case if the mixture of ML-328 (the most dwarf parents) with other parents is observed it would be clear that the mixture is invariably the intermediate. Its mean value may be closer to the taller or dwarfer parent depending upon the plants sampled for recording the observation in mixture or it may be the result of the true intergenotype interaction. These two situations may be separated out in case the mixture has the phenotypically similar lines mixed. In the present study an interesting situation has been revealed. ML-246, ML-326 and ML-419 have almost same height (97.1, 97.3 and 97.1 cm respectively). The F1s (ML-246+ML-326 and ML-246+ML-419) attained a height of 101.3 and 100.3 cm indicating that inter-genotypic competition has provided a stimulus to the growth. On the contrary the F1 (ML-246+ML-419) had an average plant height of 93.5 cm only thus indicating that a retardation has occured. It may be noted that ML-246 has figured out in both the types of inter-action thus bringing out clearly that the interaction is highly specific. While mixing the components in a multiline, it may not be enough that the height of each of the components is taken into consideration. It should in fact be superimposed with the performance. Only those lines should be mixed in the final make-up which have same height in a mixture as well. |
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