Optimizing micropropagation of Kinnow mandarin (Citrus reticulata Blanco) from shoot tip nodal segments

This study investigates the effects of various plant growth regulators on shoot and root development from shoot tip explants of Citrus reticulata cultured in Murashige and Skoog (MS) medium. The combined application of auxin (2,4-dichlorophenoxyacetic acid, 2,4-D) and cytokinin (6-benzylaminopurine, BAP) significantly influenced regeneration. The highest shoot induction rate (60%) and longest shoot length (8.00 cm) were achieved with 5.0 mg/L 2,4-D and 1.0 mg/L BAP, with visible shoot emergence as early as 8 days post-inoculation. Root induction was also optimal at the same concentration, resulting in 50% rooting, an average of 6 roots per explant, and a maximum root length of 5.00 cm. Separate evaluations of BAP and naphthaleneacetic acid (NAA) showed enhanced rooting responses at 1.00 mg/L BAP (70% rooting) and improved shoot and root growth with 1.46 mg/L NAA (30% rooting). Contamination rates remained low throughout the culture stages—8% during multiplication, 5% during shooting, and 3% during rooting—indicating reliable aseptic handling. During acclimatization, plantlets transferred to a sand:soil:compost (1:1:1) mixture exhibited the highest survival rate (90%) and robust growth. These results highlight the effectiveness of specific PGR combinations in promoting in vitro propagation and establish a reliable protocol for the large-scale regeneration and acclimatization of C. reticulata.