| In the pooled analysis, the gca/sca ratio (based on equivalent
component of mean squares) showed that gca effects were preponderant
and played an important role than sca effects for the genetic control
of days to heading, plant height, number of grains/ear, 1000-grain weight
and harvest index, hence pedigree method of breeding 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 influence of
non-additive gene effects, though these characters exhibited considerable
amount of additive genetic variance. Therefore, the improvement of such
characters warrants a breeding methodology which can exploit both additive
as well as non-additive gene effects. Under such a situation biparental
mating or recurrent selection may increase the frequency of desirable genes
and hasten the rate of genetic improvement as also reported by SRIVASTAVA
et al. 1980 and SINGH et al. 1986. Inclusion of F1
hybrids showing stable sca and having parents with good gca,
less altered by changes to environmental variations in multiple crosses,
could also prove a worthwhile approach. References GRIFFING, B. 1956. Concept of general and specific combining ability in relation to diallel crossing systems. Aust. J. Biol. Sci. 9: 463-493. JENSEN, N.F. 1970. A diallel selective mating system tor cereal breeding. Crop Sci. 10: 629-635. PARODA, R.S. & J.D. HAYS 1971. An investigation of genotype-environment interactions for rate of ear emergence in spring barley. Heredity 26: 157-175. PARODA, R.S. & A.B. JOSHI 1970. Genetic architecture of yield and components of yield in wheat. Indian J. Genet. 30: 298-314. SHARMA, S.K. & R.K. SINGH 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. SINGH, I., R.S. PARODA, & R.K. BEHL 1986. Diallel analysis for combining ability over environments in wheat. wheat Information Service 61 & 62: 74-76. SlNHA, S.K. & R. KHANNA 1975. Physiological, biochemical and genetic basis of heterosis. Advances in Agronomy 27: 123-174. SRIVASTAVA, R.B., R.S. PARODA, & O.P. LUTHRA 1980. Estimation of gene effects for components of yield in wheat. Cereal Res. Comm. 8: 515-520. |
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