Biochemical markers of morphogenesis in long term horseradish (Armoracia lapathifolia Gilib.) tissue culture

Long term in vitro cultures of plant tissue spontaneously change at morphological, cellular and biochemical level. Horseradish tissues were cultivated in vitro for more than 16 years. Primary crown-gall tumours were induced with Agrobacterium tumefaciens on leaf explants excised from plantlets propagated in vitro. Subcultured on hormone-free MS medium, transformed tissue continued to grow in an unorganized way (TN tumour) or as teratogenous tumour (TM teratoma) forming malformed shoots which never rooted. The aim of this study was to establish the morphological and biochemical status of this long term cultures. The study was performed by verifying biochemical marker of transformation and morphogenesis, which had been investigated when the culture was established (peroxidase, PPX) as well as by introducing new markers which have not been analyzed so far in horseradish tissues (ascorbate peroxidase, APX; phenylalanine-ammonia lyase, PAL; and phenolics content). Morphological changes were observed only in teratoma tissue. Peroxidase activity and isoenzyme pattern indicated stability of horseradish tissue culture. The new biochemical markers were in a complete (PAL) and partial (APX) correlation with the PPX results and are therefore useful addition in biochemical characterisation of these tissues and can also be applied as markers of morphogenesis and tumorization.