A comparative study of three different methods of shoot meristem excision for induction of embryogenic calli in coconut

A protocol was standardized to maximize yields of embryogenic calli from shoot meristem culture of coconut. Three different shoot meristem excision methods were tested viz., excision of shoot meristem aseptically from in vitro germinated embryo after 10-12 days, excision of shoot meristem from in vitro germinated embryo subjected to GA3 treatment for five days and excision of shoot meristem from fresh embryo. The primary calli induction after 30 days of culture incubation for the three treatments were 21%, 27%  and 79% respectively.  Further, the primary calli formed from the shoot meristem excised from fresh embryo gave rise to 56% of embryogenic calli. The calli obtained from the shoot meristem which were excised from in vitro germinated embryo formed less percentage of embryogenic calli because of the presence of cotyledonary tissues which inhibited the multiplication of meristematic tissues. In the case of shoot meristem extracted from GA3-treated embryos, the percentage of non-embryogenic calli was more compared to the shoot meristem excised from fresh embryo. It was observed that the addition of GA3 in the initial stages of culture inhibited the formation of embryogenic calli and favored direct shoot development. Currently, the shoot meristem excised from fresh embryo is being employed for scaling up the planting material production from released varieties of coconut

Virtual screening and <i>in vitro</i> evaluation of potential growth regulators against somatic embryogenesis receptor-like kinase (SERK) in <i>Cocos nucifera</i> L.

328-340Coconut (Cocos nucifera L.) is one of the most recalcitrant species for in vitro regeneration and the efficiency of induction of somatic embryogenesis in coconut explants has remained low. However, with the advent of the genomics era, more information is now available on the involvement of many genes in the induction of somatic embryogenic pathway. Somatic embryogenesis receptor-like kinases (SERKs), belonging to leucine-rich repeat receptor-like kinase super family are reported to play important roles in the process of somatic embryogenesis. In this study, homology based modeling and molecular dynamics (MD) simulation of a coconut SERK protein (CnSERK) was performed for exploring its structural features, functional characterization of its active sites and binding mechanisms of selected plant hormones and growth regulators by docking studies. The 3-D model for coconut SERK was constructed using structure neighbors of the protein in MODELLER and MD simulation was carried out using GROMACS for 5 ns. Fifteen plant growth regulators were docked with the target SERK protein using GLIDE software. An in vitro study was then carried out to compare the efficiency of three selected chemicals [adenine sulphate, glutathione and 22(S), 23(S)-homobrassinolide] in enhancing somatic embryogenesis from plumular explants of coconut. Plumular explants were from West Coast Tall cultivar of coconut and were inoculated into Eeuwens Y3 media supplemented with various concentrations of each of the three growth regulators. Among the three growth regulators, glutathione (100 µM) gave the best response for induction of both embryogenic calli and somatic embryogenesis. The results of this study might aid in the development of regeneration protocols for in vitro regeneration in coconut