Division of Genetics, Indian Agricultural Research Institute, New Delhi
*Paper based on a part of the data submitted to the Post Graduate Faculty, I.A.R.I, in partial fulfilment of the requirements for the Ph.D. degree by P. L. N. SOMAYAJULU.
A PDC with 23 wheats and s=4, omitting reciprocals, was made according to the design suggested by Kempthornc and Curnow (1961). The strains were selected on the basis of genetic divergence as estimated by the Mahalanobis's D2-statistic in a previous study, geographic diversity and previous knowledge of the breeding value.
ANOVA of the PDC revealed significant gca variances for grain yield, flowering time, ears per plant, 250-grain weight and spikelets per car, indicating possible response to selection in respect of these characters. Such a possibility was not evident for grains per ear and synchrony of tillering. However, the sca variances were also substantial for all the characters studied.
The possibility of changes in the estimates with changes in the random order of listing of the parental strains in determining the sampled crosses is recognised. However, the correspondence between the gca estimates obtained and past breeding experience with some of the varieties assessed and the agreement observed between the estimates based on the F1 and F2 data collected in two different environments, seem to justify a degree of confidence in the utility of the PDC estimates.
The results indicate that, among the varieties studied, E. 952, E. 871, E. 5175, N.P. 830, Hyb. 65 and E. 957, are likely to be the best for use in breeding for high grain yield, provided other factors do not limit a full realisation of their apparent genetic potential. The high gca estimates of these varieties for grain yield are supported by similar estimates for one or more characters influencing grain yield.
