The genotype differences in callus induction, growth and morphogenetic potential indicate genetic determination of these characters. Therefore, we analyzed the genetic determination of somatic callogenesis in a diallel cross and studied genetic correlations between characters in vitro and in intact plants. In the diallel cross 6 inbreds with different growth rates of callus were included. Kernels of the F1 generation from the diallel cross were used both for induction of callus culture from mature embryos and for field trials.

A different degree of heterosis (in comparison with population mean, 52.7 - 198.65%) was found in growth rate of callus culture of F1 hybrids. Statistically significant differences were observed between hybrids from direct and reciprocal crossing. The highest degree of genetic variability was due to GCA, and the effect of reciprocals was also important:
 

Source	df	Mean square	F
GCA	5	1.1778	19.62**
SCA	15	0.8302	6.00**
Reciprocals	15	1.2726	7.8**
Residual	432	74.9167

The correlation analysis on the level of inbreds showed strongly negative dependence between the callus weight and kernel yield (r = -0.811**) and ear localization on the plant (r = -0.604**). Positive correlation was found between the callus weight and the leaf area (r = 0.729**). The correlation relationships on the hybrid level were impaired both by a different degree of heterosis effect on the in vitro characters and the characters of intact plant and by reciprocal differences occurring only in the callus weight.

The results of the diallel cross and correlation analysis indicate that the growth of callus is under genetic control of two genetic systems; one is localized in the nucleus and the other in cytoplasm.

M. Nesticky, F. J. Novak,* A. Piovarci, M. Dolezelova*

*Institute of Experimental Botany, CSAV Olomouc

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