Coleoptilar node - A season-independent explant source for in vitro culture in maize (Zea mays L.)

Abstract

In vitro plant regeneration is preliminary requisite in the process of obtaining transgenic plants. Somatic embryogenesis is the most frequently used method of in vitro plant regeneration in maize. In this study, a reliable and reproducible maize regeneration method has been standardized using mature embryos. Inspite, the immature embryos are most suitable explants for somatic embryogenesis, obtaining these explants continuously is a laborious and tedious process, especially in summer. Hence, alternate explants of maize for in vitro regeneration have been chosen from different parts of embryonic axis. This study provides an evaluation of inbred lines and effect of hormonal combinations on total and embryogenic callus induction, their growth rate, and plantlet regeneration. Coleoptilar nodal explants from four inbred lines were cultured on different concentrations and combinations of 2,4-dichloro phenoxyacetic acid (2,4-D) along with kinetin (Kn). Explants grown on Murashige and Skoog medium supplemented with 2,4-D and Kn at a concentration of 5 and 1 mg/L, respectively, were found to be the best one for yielding a high frequency of embryogenic callus. Inbred line, NM81A was found to be the best one for in vitro culture among the four lines used. Combination of 6-benzylaminopurine and Kn at a concentration of 1 mg/L each promoted the highest frequency of shoot induction.

Development of stable transgenic maize plants tolerant for drought by manipulating ABA signaling through Agrobacterium-mediated transformation

“…Genotype is also critical and associated with the explant for in vitro growth and regeneration. Sridevi et al [19] reported that inbred line NM5884 is suitable for using IEs as explants, whereas another inbred line NM74C has been reported suitable for using coleoptilar node as an explant [45]. In the present study, it has been further confirmed that NM5884 is the most suitable genotype for using IEs not only for in vitro studies but also for genetic transformation in maize.…”

“…As maize is an important crop with a wide range of utilization as food and fodder, extensive exploration of suitable conditions and materials for the development of the crop has been done. For in vitro studies and transformation, almost all the plant parts have been used viz., immature tassels [40], shoot tips [41,42], germinated split seeds [43], mature embryos [44], and coleoptile nodes [36,45]. Among all the explants of maize used, immature embryos were found to be the best explants in most of the studies [46,47].…”

“…Media and its components play important role for in vitro growth and regeneration, mostly MS media was used for different explants. Abbas et al [55], Sreenu et al [36], and Pavan Kumar et al [45] established the in vitro cultures and Agrobacterium-mediated transformation protocols by using MS medium with coleoptilar nodal explants in maize. In the present study, the LS medium has been used and found to be more suitable for the immature embryos, which has also been reported in earlier studies [16,19].…”