Physiological ageing during prolonged in vitro-culture of multiple shoots of Bambusa bambos var. gigantea Bennet and Gaur

Abstract

SummaryThis report describes the extent of physiological ageing under in vitro-culture conditions in multiple shoots of Bambusa bambos var. gigantea depending on shoot multiplication rate (MR), rooting capacity, and rhizome induction. The occurrence of physiological ageing undermines the viability of clones obtained by prolonged micropropagation over long periods of time. Multiple shoots induced at the embryonic axes of caryopses were sub-cultured continuously (4 weeks per culture) and alternately on Murashige and Skoog (MS) medium containing 5.0 µM 6-benzylaminopurine (BAP) or containing 5.0 µM BAP plus 0.1 µM gibberellin (GA3). The rate of shoot multiplication declined after 13 – 20 sub-cultures and could not be reversed by substituting thidiazuron (TDZ) for BAP, or by adding a lower concentration of BAP (2.5 µM) to the medium to overcome any dosage tolerance caused during repeated sub-culturing. Multiple shoots that formed after 13 sub-cultures became necrotic, even after root formation on MS medium containing 0.1 – 50.0 µM α-naphthaleneacetic acid (NAA), possibly because of physiological ageing.After sub-culture-11, in vitro-raised shoots of B. bambos var. gigantea exhibited prolific multiplication on 5.0 µM BAP, poor rooting on either 10.0 or 25.0 µM NAA, and rhizome-formation on MS medium containing 50.0 µM NAA plus 0.2 mM boric acid. These observations provide evidence for physiological ageing.