Efficient micropropagation of <i>Citrus sinensis</i> (L.) Osbeck from cotyledonary explants suitable for the development of commercial variety

Abstract

In vitro regeneration of sweet orange (Citrus sinensis (L.) Osbeck Family: Rutaceae) has been performed via direct and indirect organogenesis. For indirect organogenesis, callus was induced and proliferated from leaf explants derived from in vitro grown seedlings on Murashige and Skoog (MS) media containing 2,4-dichlorophenoxyacetic acid (2,4-D) alone or in combination with benzyl adenine (BA) and α-naphthalene acetic acid (NAA). For direct organogenesis, explants were placed on MS media containing BA alone or in combination of NAA and gibberellic acid (GA₃). Well-developed microshoots were treated with different concentrations of NAA for rhizogenesis (a two-step procedure). Different responses to these treatments were recorded depending upon the procedure used. It appears that 4.53 μM 2,4-D in combination with 5.37 μM NAA induced 93.33% callus and proliferate 86.67% of callus into 6.93 shoots per explant. Exogenous addition of 4.44 μM BA in combination with 1.54 μM GA₃ enhanced shoot multiplication rate significantly (17.73±1.69 shoots/explant) in comparison to control (0.00±0.00 shoots/explant). Microshoots were rooted best (75.00±14.43%) under the treatment 100μM NAA for 48 hrs. and rooted plantlets were transferred to soil, following acclimatization were taken to maturity in the polyhouse.

Keywords: Malta, Himalaya, benzyl adenine (BA), callus