Studies on callus growth and morphogenesis in several species and lines of t Amaranthus

A study has been carried out on several Amaranthus L species and breeding lines (A. caudatus, A. cruentus, A. hybridus, A. hypochondriacus), some of which have previously shown poor or no plant regeneration from callusing primary explants. Callus formation occurred from explants from almost all the lines tested. Significant differences in callus growth were observed among the lines depending on the growth regulator combinations used. Cultural conditions such as type and growth regulator combination, as well as age-dependent competence of the explant tissues, 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 genotype, growth regulator dose and combination, the type and the physiological stage of explant are factors of great importance for in vitro plant regeneration. This revised version was published online in June 2006 with corrections to the Cover Date.