PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Maize (Zea mays L.) is an important cereal crop with substantial value for food, feed and industrial applications. However, the efficiency of in vitro regeneration in maize is often influenced by genotype, explant type and culture conditions, which can limit the reproducibility of tissue-culture-based approaches. Therefore, developing an efficient callus induction system using readily available nodal explants is important for establishing a reliable foundation for subsequent regeneration and related biotechnological applications. This study evaluated an in vitro callus induction protocol for maize (Zea mays L.) genotype CML1514 using split nodal explants. Healthy nodal segments were excised from 7- to 10-day-old in vitro-raised seedlings and cultured on Murashige and Skoog (MS) medium supplemented with different concentrations and combinations of plant growth regulators. Seeds were surface sterilised with Tween-20 followed by 0.1% mercuric chloride and germinated in vitro prior to node excision; the excised nodes were further surface sterilised with 70% ethanol before culturing. For callus induction, nodal explants were cultured on MS medium containing ten combinations of 2, 4-dichlorophenoxyacetic acid (2, 4-D; 1.0-5.0 mg/l) with either 6-benzylaminopurine (BAP; 1.0-2.0 mg/l) or kinetin (1.0-2.0 mg/l). Among the tested treatments, MS medium supplemented with 5.0 mg/l 2, 4-D and 2.0 mg/l BAP showed the strongest callusing response, with callus initiation observed within 5.7 days and a callus formation frequency of 93.3%. BAP consistently promoted faster callus initiation than kinetin across all 2, 4-D concentrations tested. Of the ten media combinations, six produced compact, embryogenic callus, while the remaining four produced soft, non-embryogenic callus. The study indicates that nodal explants can be used for rapid, high-frequency callus induction in CML1514, providing a reliable foundation for subsequent somatic embryogenesis and plant regeneration. All experiments were conducted in triplicate and the data were subjected to appropriate statistical analysis.