Lysine-threonine inhibition in callus culture

In the previous work (Nesticky et al., Z. Pflanzenz. 86:33-40) the possibility of using lysine-threonine inhibition in embryo culture was studied. From the inbred lines used in this study, inbred line MT42 and its opaque-2 analogue were chosen to verify this inhibition on the level of callus culture in vitro. Callus cultures were initiated from the excised embryos of mature kernels on basal medium MS. During three subcultures, callus growth on selective medium with 2 MM lysine and 1 mM threonine was observed.

Callus growth of the opaque-2 analogue on the selective medium reached on average 30.1% in comparison with the control. Within every subculture, callus growth varied from 19.4% to 45.5%. Callus growth of the normal analogue on the selective medium with lysine and threonine reached 61%. This means that the growth of the opaque-2 analogue on selective medium was two-fold less than normal.

This result is in contradiction with our previous study, in which the opaque-2 analogue in embryo culture with exogenous lysine and threonine significantly outgrew the normal analogue. This disagreement in results cannot be explained by the already known hypotheses of Rapela (MNL 55:54, Plant and Cell Physiol. 23:285-291 and Phillips et al. (Crop Sci. 21:601-607) because both results were obtained on the same genotype. Knowing the results of Lukjanuk and Ignatova (pers. commun.), it is possible that the ontogenetic stage and/or level of differentiation of explant will play a role in the expression of inhibition in one genotype. Study of this problem is in progress.

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

*Institut of Experimental Botany, CSAY Olomouc

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