A Useful Pathway for Gnetum Planting Material Production: Effect of Exogenous Application of Auxin on Root and Shoot Expression of Gnetum Cuttings

Abstract

Cutting’s rooting and budding are one of the main constraints for the domestication and cultivation of G. africanum and G. buchholzianum. The effects of exogenous indol-3-acetic acid (IAA) and indol-3-butyric acid (IBA) on rooting and budding from cuttings of both lianas were studied. Fresh cuttings of both lianas were soaked for 12 h in DKW mineral complex supplemented with varying concentrations (0 mg L⁻¹, 50, mg L⁻¹ 100 mg L⁻¹, 150 mg L⁻¹, and 200 mg L⁻¹) of IAA and IBA. The above-treated cuttings were sown in propagators and monitored for eight weeks. Auxins’ treatment of cuttings significantly improves roots and bud’s expression of cuttings from both liana species. Compared to their respective controls (5.11 ± 0.74% and 7.06 ± 1.60%), rooting response of cuttings was significantly improved in G. africanum (IAA:23.11 ± 3.54% P_v = 0.039; IBA:37.28 ± 6.47%, Pv = 0.076) and G. buchholzianum (IAA:32.42 ± 4.31%, Pv = 0.009; AIB: 30.16 ± 4.08%, Pv = 0.021). Best rooting (59.22%) and budding (57.77%) response was obtained respectively with IBA 150 mg L⁻¹ and 100 mg/L⁻¹ in G. africanum. IBA allowed the development of the longest root (9.2 cm) and highest number of roots (12 roots/cutting) respectively with 100 mgL⁻¹ and 150 mg L⁻¹. Hence, exogenous IBA (100 mg L⁻¹ and 150 mg L⁻¹) and IAA (100 mg L⁻¹) are suitable for root induction and expression in both lianas. However, 100 mg L⁻¹ IBA appeared to be efficient in stimulating budding in studied lianas. This technical pathway is useful for planting material production from G. africanum and G. buchholzianum cuttings. The obtained planting material were found suitable for farm establishment.