The gca/sca ratio (based on equivalent component of mean squares) in the pooled analysis indicated that gca effects were predominant and played a more important role than the sca effects in exercising genetic control for days to heading, plant height, number of grains/ear and 1000-grain weight, hence pedigree method of selection can be used for the improvement of these characters. Contrary to it, characters like tiller number, total biomass and grain yield were mainly under the control of non-additive gene action, though they also showed considerable amount of additive genetic variance. Improvements of such characters warrants for a breeding methodology which can capitalize additive as well as non-additive genetic variance. In this situation biparental mating offers good promise to increase the frequency of genetic recombination and hasten the rate of genetic improvement (Gill et al. 1972; Srivastava et al. 1980). Inclusion of F₁ hybrids showing stable sca and having parents with good gca, less altered by changes to environmental variations into multiple crosses, could also prove a worthwhile approach.

References

GILL, K. S., DHILLON, S. S. and BAINS, K. S. 1972. Combining ability and inheritance of yield components in crosses involving Indian and exotic wheat germplasm. Indian J. Genet. 32, 321-430.

GRIFFING, B. 1956. Concept of general and specific combining ability in relation to diallel crossing systems. Aust. J. Biol. Sci. 9, 463-493.

PARODA, R. S. and HAYS, J. D. 1971. An investigation of genotype-environment interactions for rate of ear emergence in spring barley. Heredity 26, 157-175.

PARODA, R. S. and JOSHI, A. B. 1970a. Genetic architecture of yield and components of yield in wheat. Indian J. Genet. 30, 298-314.

PARODA, R. S. and JOSHI, A. B. 1970b. Combining ability in wheat. Indian J. Genet. 30, 630-637.

SHARMA, S. K. and SINGH, R. K. 1982. Diallel analysis for combining ability over environments in wheat. Haryana agric. Univ. J. Res. 12, 675-678.

SINGH, D. 1973. Diallel analysis for combining ability over several environments-II. Indian J. Genet. 33, 469-481.

SINHA, S. K. and KHANNA, R. 1975. Physiological, biochemical and genetic basis of heterosis. Advances in Agronomy 27, 123-174.

SRIVASTAVA, R. B., PARODA, R. S. and LUTHRA, O. P. 1980. Estimation of gene effects for components of yield in wheat. Cereal Res. Comm. 8, 515-520.

1) Present address: Director, National Bureau of Plant Genetic Resources, New Delhi-110012, India.

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