STUDIES ON CALLUS GROWTH AND MORPHOGENESIS IN SEVERAL SPECIES AND LINES OF AMARANTHUS

A study has been carried out on several Amaranthus L species and breed ing lines (A. caudatus, A. cruentus, A. hybridus, A. hypochondriacus), some of which have previously shown poor or no plant regeneration fro m callusing primary explants. Callus formation occurred from explants from almost all the lines tested. Significant differences in callus gr owth were observed among the lines depending on the growth regulator c ombinations used. Cultural conditions such as type and growth regulato r combination, as well as age-dependent competence of the explant tiss ues, also influenced the frequency of shoot (and/or root) regeneration in Amaranthus species that had been shown difficult to regenerate in the past. The results obtained demonstrate that in Amaranthus the geno type, growth regulator dose and combination, the type and the physiolo gical stage of explant are factors of great importance for in vitro pl ant regeneration.