*Part of Ph.D. Thesis submitted by senior author to Kanpur University, Kanpur during 1976.
Combining abilities of F1 and F2 generations of crosses involving 10 diverse derivatives of wheat were analysed for 11 traits related to productivity. ANOVA for combining ability revealed that both g.c.a. and s.c.a. variances were significant except s.c.a. variance for days to maturity at F2 level. The magnitude of estimates for g.c.a. variances were lower than that of s.c.a. variances for all the traits except for days to maturity (F1 and F2) and plant height in F1 generation reflecting the predominance of non-additive genetic component for grain yield per plant and its related developmental as well as component traits.
The relative ranking of parents on the basis of per se performance and g.c.a. effects suggested that the parents K 816, HD 1949, K 813 and Kalyansona were best general combiners in both the generations when 5 to 6 traits out of 10, related to development and productivity were considered at a time. The next parent in order of merit was SP 1 which was also good general combiner for 4 developmental traits in F1 and F2. An appraisal of 5 best combiners indicated that all these parents were derivatives of wheat crosses involving dwarf genes in their back-ground. Since these 5 parents in both the generations were superior for several characters either an inter-mating population among themselves or using biparental mating in early generation may offer maximum scope for breeding for high grain yield. As judged from significant and desirable s.c.a. effects for yield, 13 and 6 crosses in F1 and F2 generation, respectively involved all three possible combinations between the parents of high and low g.c.a. effects. The cross ‘K 853 × Kharchia’ in F1 ‘K 853 × Hyb 65’ in F2 came in the category where both parents had high g.c.a. effects. Out of these, K 853 x Kharchia, of F1 showed low s.c.a. effect in F2 indicating the presence of dominant type of gene action. The other cross, ‘K 853 x Hyb 65’ showed average s.c.a. effects in F1 and high mean coupled with significant s.c.a. effects in F2 reflecting the presence of additive x additive inter-action effects. The other nine cross combinations involving atleast one parent with significant g.c.a. effects may throw out desirable transgressive segregates. In order to utilized them efficiently, it is suggested to undertake inter se crossing for multiple parents input into a central gene pool which will accelerate the faster speed of genetic recombinations and also help in breaking linkage blocks, being broad-base-gene pools it aids in freeing of latent genetic variability. These crosses also exhibited desirable s.c.a. effects for 4 to 7 traits out of 10 studied.
