In Vitro Protocol Optimization for Micropropagation of Promising Ginger (Zingiber officinale Rosc.) Accession 52/86 from Sprouted Rhizome Buds

Abstract

Ginger is one of the important cash crops in Ethiopia. However, unavailability of disease free planting material (rhizomes), poor flowering and seed sets are the major problems in ginger propagation. Tissue culture is the best option to overcome these problems, since it is propagated under aseptic area to reduce disease transmission. Therefore, this study was initiated to optimize protocol for micropropagation of ginger accession 52/86 under in vitro conditions. Murashige and Skoog (MS) basal medium was used in this study. For culture initiation, sterilized sprouted rhizome bud was used and data were collected on number of initiated shoots. In vitro shoot multiplication, five different concentrations of 6-benzylaminopurin (BAP) and four concentrations of kinetin (KN) in a 5 x 4 factorial combination treated with three replications and five explants per jar were used in completely randomized design (CRD). Data were collected on number of shoot per ex-plant, shoot length and number of leaves per shoot. In rooting experiment, five different concentrations of α-Naphthalene acetic acid (NAA) and four concentrations of Indole-3-butyric acid in a 5 x 4 factorial combination treated with three replications and five explants per jar were used in CRD. Data were collected on root number per shoot and root length. Acclimatization was done on six different soil media combined as treatments with 10 plantlets per pot with three replications in greenhouse using CRD. Data were collected on numbers of survived plantlets in greenhouse from each soil media. The results showed that from well sterilized sprouted rhizome buds up to 91.3 % initiated shoots were achieved. On shoot multiplication, maximum shoots per ex-plant (9.34±0.55) were obtained on a medium containing 2.5 mg/L BAP + 1.0 mg/L KN. The largest shoot length (5.10 ± 0.17 cm) was obtained on MS medium containing 2.5 mg/L BAP + 0.5 mg/L KN growth regulators. The highest mean number of leaves per shoot (5.67± 0.06) was obtained on a medium containing 3.0 mg/L BAP+0.5 mg/L KN. The highest mean number of root per shoot (12.60±0.17) was achieved on a medium supplemented with 2.5 mg/L NAA + 1.0 mg/L IBA and largest root length (6.30±0.10 cm) was achieved on a medium containing 1.0 mg/L NAA + 1.0 mg/L IBA hormones. Among soil combined for the plantlets acclimatization, the highest survival percentage (98 %) was recorded on top soil (TS): sandy soil (SS): coffee husk (CH) (1:1:1). Thus, MS + 2.5 mg/L BAP + 1.0 mg/L KN and half MS+ 2.5 mg/L NAA + 1.0 mg/L IBA were the best hormone combination for shoot multiplication and in vitro rooting, respectively. At greenhouse, media combination of TS: SS: CH (1:1:1) ratio was found to be optimal for plantlets acclimatization. Therefore, the optimized protocol can be used for rapid multiplication of the clean planting materials for ginger accession 52/86.