Rooting Responses of Miracle Fruit (Synsepalum dulcificum) Softwood Cuttings as Affected by Indole Butyric Acid

Abstract

Large scale productions of miracle fruit (Synsepalum dulcificum) faces some restrictions as the seeds are recalcitrant and propagation by cuttings is difficult to root. When grown from seed, miracle fruit takes 3 to 4 years to begin fruiting. A propagation technique by cuttings needs to be devised to produce early fruiting planting materials. However there has been no report on the rooting performance of miracle fruit stem cuttings using Indole-3-Butyric Acid (IBA) and the location of root primordia initiation is unknown. Softwood miracle fruit cuttings were treated with five IBA concentrations (0, 200, 400, 600 and 800 mg L^-1) and placed in a propagation area with intermittent mist. Data for percentage of rooting (%), mean root numbers per rooted cutting, mean root length per rooted cutting (cm) and root dry weight per rooted cutting (g) were collected 3 months after planting. Thirty softwood cuttings were propagated for histological study. The basal 5 mm of three cuttings were harvested randomly weekly. The specimens were sectioned and the cross sections were viewed to locate the root primordia initiation. Callus formation started three weeks after sowing and the adventitious roots emerged from the basal end eight weeks after planting. High concentration of IBA treatment was significantly increase the rooting percentage when compared with other treatments. Anatomy of stem 800 mg L^-1 day 0 showed the phloem was surrounded by 2-3 layers of fibers. Root primordial developed from the secondary phloem and penetrated the fiber layers 5 weeks after planting. IBA concentrations gave little effect in roots initiation and development of miracle fruit. Root primordial was developed from the secondary phloem and surrounded by fiber layers was could hinder its emergence. However, IBA applications promoted cell expansion and proliferations which able to break the fiber layers and allowed the root primordial to emerge.