Genetic variation for protein concentration in a random mating opaque-2 variety of maize

The variability for protein concentration in a composite cultivar named "Rattan" was studied using half sib and full sib progenies developed by following nested mating design (Design-1 of Comstock and Robinson, Biometrics 4:254-266, 1948). Sixty-four plants were selected at random and each as a male was crossed to four randomly taken plants used as females, making 64 half sibs and 256 full sibs. These were grown in two agro-climatically different locations in an incomplete block design with two replications.

Table 1. The estimates of various variance components along with standard errors
Variance components Pooled Location I Location II
Additive genetic 0.01 ± 0.12 -0.19 ± 0.17 -0.71 ± 0.32
Dominance -0.03± 0.33 1.86 ± 0.44** 4.53 ± 0.94**
Additive x environment -0.40± 2.40 - -
Dominance x environment 3.80 ± 0.96** - -
**Significant at 1 percent probability level

Perusal of Table 1 indicates that only dominance variance component was significant in the individual locations analysis. However, in the pooled analysis the only component that was significant was due to dominance x environment interaction. Negative estimates were also obtained contrary to the theoretical expectations. The results indicated that the population is not suited for protein improvement through intra-population selection. It may be added that remarkable progress has been made in the manipulation of protein concentration in "Burr White" in a classical long-term selection experiment at Illinois (Dudley, pp. 459-473, in Proc. Internat. Conf. Quant. Genetics, Pollak et al., eds., Iowa State Univ. Press, Ames, 1977).

S. S. Pal, A. S. Khehra, B. S. Dhillon and K. S. Sekhon

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