| 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 1,000-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 nonadditive 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 and SRIVASTAVA et al. 1980). In clusion 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. & BAINS, K.S. 1972. Combining ability and inheritance of yield components in crosses involving Indian and exotic wheat germplasm. Indian J. Genet. 32 : 421-430. 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. & 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. & JOSHI, A.B. 1970a. Genetic architectuzre of yield and comoponents of yield in wheat. Indian J. Genet. 30 : 298-314. PARODA, R.S. & JOSHI, A.B. 1970b. Combining ability in wheat. Indian J. Genet. 30 : 630-637. SHARMA, S.K. & 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. & KHANNA, R. 1975. Physiological, biochemical and genetic basis of heterosis. Advances in Agronomy 27 : 123-174. SRIVASTAVA, R.B., PARODA, & R.S. LUTHRA, O.P. 1980. Estimation of gene effects for components of yield in wheat. Cereal Res. Comm. 8 : 515-520. |
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