Induction of embryogenic calli from immature ovaries in coconut (cocos nucifera L.)

Abstract

The study entitled " Induction of embryogenic calli from immature ovaries in coconut (Cocos nucifera L.)" was conducted at the Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, Thiruvananthapuram during 2022-23. The objective of the study was induction of embryogenic calli from immature ovary in coconut variety West Coast Tall (WCT) and effect of sodium butyrate in callus induction through histone deacetylation. In the present study, immature ovaries from explants of maturity indices 4 to -6 were extracted and surface sterilized using 3% sodium hypochlorite, 0.2% mercuric chloride, and 70% ethanol. They were inoculated into basal Y3 medium containing different plant growth regulators such as 2,4-D, TDZ, and picloram. The results showed that out of all the maturity indices tried (-4 to -6), inflorescence of maturity index -4 showed a maximum response in callus induction, and among different callus induction medium (CIM) tried CIM with 100 μM 2,4-D showed maximum response (47.28%) to embryogenic calli initiation. The time taken for embryogenic calli-like structure development was 45 days. To analyze the effect of sodium butyrate (SB) in callus initiation, the excised immature ovaries were inoculated into standardized CIM (Y3 + 100 μM 2,4-D) with different concentrations of SB. The results displayed that, compared with the CIM, the induction rates of embryogenic calli were significantly increased (66%) and the time taken for embryogenic calli-like structure development was significantly reduced (20 days) with the addition of 100 μM SB. The gene expression analysis shows that gene expression of the HDA6 gene was reduced in CIM with SB when compared to CIM. The increased embryogenic response of immature ovaries to CIM with SB as well as the reduced time taken for the embryogenic response can be correlated with the downregulation of the HDAC gene.