In vitro propagation of big - leaf mahogany (Swietenia macrophylla king through tissue culture.

Abstract

The study entitled “In vitro propagation of big-leaf mahogany (Swietenia macrophylla King) through tissue culture” was carried out at the Tissue Culture Laboratory of College of Forestry, Vellanikkara during the period 2007-2009. The objective of the programme was to standardize a protocol for in vitro micropropagation of big-leaf mahogany (Swietenia macrophylla King).

Fungal contamination was found to be prominent in rainy season and was a major problem in establishing the aseptic cultures of mahogany through axillary bud break. Explants collected during November to April were shown less percentage of contamination. To establish contamination free cultures, explants were pretreated with a fungicidal solution of Bavistine (Carbendazim) and Indofil M-45 (Moncozeb) each at 0.2 percent for 1 hr and followed by surface sterilization with 0.1 percent mercuric chloride for 15 minute. During the present investigation, season of explant collection has also influenced the culture establishment and growth.

Out of the three media employed, viz. MS, WPM and B5, MS medium was found to be suitable for culture establishment and growth. Murashige and Skoog media was used for further studies, fortified with different plant growth regulators (PGR) viz. cytokinin (BA and Kinetin) and auxin (IAA and IBA). Cytokinins at different concentrations (0.5, 1.0, 2.0 and 3.0 mg l-1) were supplied individually or in combinations with auxins at various concentrations (0.1, 0.5 and 1.0 mg l-1).

Kinetin supplemented alone to MS at higher concentrations was found to be enhancing bud initiation when compared to its counterpart BA which was effective, when supplied alone at lower concentrations. For multiple shoot production supplementation of BA to MS medium was more effective than kinetin. Benzyl adenine fortified in combination with IAA was effective for culture establishment and growth from axillary buds of mahogany, over other combinations such as BA + IBA, kinetin + IAA and kinetin + IBA. Murashige and Skoog media supplemented with 2.0 mg l-1 BA+0.1 mg l-1 IAA was found to be best suited for bud initiation, shoot proliferation and leaf initiation. However, maximum number of shoots (3.33) was recorded on MS media supplemented with 1.0 mg l-1 BA along with 0.5 mg l-1 IBA.

Subsequent production of multiple shoots from microshoots of primary cultures through sub culturing failed due to shoot elongation and abscission of leaves in sub cultures. Due to such obstacles rooting experiments were not carried out and hence, a precise and profitable protocol for in vitro micropropagation of mahogany could not be developed in the present study.