Commercial production of ginger (Zingiber officinale ROSC) microrhizomes using temporary immersion bioreactor system

Abstract

Ginger (Zingiber officinale Rosc.), is an important commercial spice crop grown in India from very ancient times. High seed rate of ginger (1500 kg/ha) and desiccation of seed rhizomes during storage are the problems faced by farmers in ginger cultivation. The tissue culture plants are not commercially distributed in ginger as they require an additional one more season for rhizome formation. Microrhizomes of ginger induced in vitro if used as planting materials, rhizomes can be harvested in the same season as conventional seed rhizomes and year round availability of seed material can be ensured. Hence, in vitro induced microrhizomes are included in the seed chain of ginger and there is high demand for microrhizomes for clean ginger production. The study entitled “Commercial production of ginger (Zingiber officinale Rosc.) microrhizomes using Temporary Immersion Bioreactor (TIB) system” was conducted at Centre for Plant Biotechnology and Molecular Biology (CPBMB), College of Horticulture, Vellanikkara during 2018 to 2020. The objective of the study was to develop an efficient commercial production protocol for ginger microrhizomes using a TIB system. The study was conducted in the ginger variety Athira using Plantform TIB purchased from Sweden. The multiple shoot cultures in the 5th subculture stage received from the commercial micropropagation unit, of CPBMB were used for the study. The protocol for in vitro induction of microrhizomes reported by Shylaja et al. (2016) was optimised for bioreactor production and at each stage it was compared with the conventional microrhizome production. The number of clumps/ 500ml of medium to initiate multiple shoot production, media for shoot multiplication and microrhizome induction were optimised for TIB and compared with conventional microrhizome production system. The microrhizome, root and shoot characters in microrhizome plantlets and growth of microrhizome plants after hardening were evaluated in the two culture systems. The clonal fidelity analyses of microrhizome plants derived from 8th subculture cycle were done using the specific ISSR marker as reported by Gavande, (2013). The clump size of 15 clumps/ 500 ml of medium showed higher shoot multiplication in both TIB and conventional system. The shoot proliferation in bioreactor (7.71 shoots/clump) was significantly higher than the conventional microrhizome production system (5.24 shoots/clump). Early induction of microrhizomes was observed in TIB system. In both the culture systems, microrhizome induction was faster in MS medium with 90 gL-1 sucrose. The number of microrhizomes produced in the medium in TIB varied from 87.75 to 96.75/ 500ml medium and in conventional system it varied from 84 to 88/ 500 ml medium. The microrhizome plantlets produced in TIB recorded significantly higher weight of microrhizomes, better shoot and root growth and more number of leaves compared to the microrhizome plantlets produced in the conventional system. The weight of microrhizomes, number of roots and root length were higher in microrhizome plantlets in MS medium with 90 gL-1 sucrose. The mean weight of microrhizome in the medium was 0.29 g in bioreactor and 0.18 g in conventional system. The survival of microrhizome plants after primary hardening was 94.34 per cent and after secondary hardening was 99.29 per cent in TIB. Microrhizome plants from bioreactor recorded significantly higher plant height (18.60 cm) compared to conventional system (14.80 cm). The number of leaves recorded in microrhizome plants of both the culture systems were on par and ranged from 6.97 to 7.18. Clonal fidelity analyses using specific ISSR marker revealed that there were no polymorphism in the ISSR amplification profiles in microrhizome plants produced after the 8th subculture cycle with the source mother plant and hence plants produced from both the culture systems are true to type. The protocol developed in the present study can be further modified by early bulking of the clumps, employing TIB for multiple shoot production in early culture phase and reducing the number of culture cycles so that the entire protocol period can be reduced. Evaluation of TIB microrhizome plants in high tech poly house or field and comparison of yield and quality with microrhizome plants from conventional production system also can be focused for further research.