Plant regeneration via somatic embryogenesis and direct shoot organogenesis of a C4 bioenergy crop Pennisetum pedicellatum Trin.

Abstract

Pennisetum pedicellatum Trin. is a C4 tropical perennial forage grass known as Deenanath grass holding great potential to address vital, puzzling issues such as bio-economy, human health and the environment. Genetic complexity not only is a big barrier in selection and breeding practices but also restricts harnessing of the full potential of this multipurpose fodder crop. By optimizing a rapid, effective and consistent in vitro regeneration protocol through callus mediated and direct shoot organogenesis, we can multiply these plants for producing a large amount of biomass. Calli were induced from mature seeds and shoot apices of two genotypes on Murashige and Skoog (MS) medium containing different levels of 9.0–22.5 µM 2,4-Dichlorophenoxyacetic acid (2,4-D) and a constant level of 2.22 µM N6-benzyladenine (BA). Seventy-one percent of the calli turned embryogenic when 2,4-D (2.25 µM) was reduced in the medium. Somatic embryogenesis was accomplished on MS medium with an increased level of either BA (4.4–17.6 µM) or kinetin (4.6–18.4 µM) along with 0.56 µM 2,4-D. Ultra-structural and histological studies indicated globular, scutellar and coleoptilar somatic embryos. A maximum of 82.7±1.6% plant regeneration was accomplished from seed explants on MS medium containing 8.8 µM BA and 0.56 µM 2,4-D. Multiple shoots were induced on MS media containing either BA (4.4–18.0 µM) or kinetin (4.6–18.4 µM) along with 0.56 µM 2,4-D using shoot apices. A maximum of 22.1±0.45 shoots per shoot apex was produced on MS medium containing 8.8 µM BA and 0.56 µM 2,4-D. Successful rooting of healthy shoots generated through both the pathways could be optimized on ½MS medium containing 0.4% charcoal. Complete plants could be hardened in plastic pots and were well established on field conditions. In vitro regeneration was established for the first time successfully, which would be very useful for genetic improvement of this apomictic species through transgenic approach.