In vitro regeneration of Begonia homonyma — A threatened plant

Begonia spp. is the fifth largest angiosperm and can be used well as a disinfectant. It cleans wounds excellently. It can reduce swelling and can be used in a variety of diseases. The rhizome of the plant is a good antibacterial agent. It is often used against diarrhoea, bronchitis, colds and digestive disorders. The leaves of the plant are often used as vegetables or for teas[1].

What kind of explant was the starting point for the ongoing investigation?

The starting point for the investigation was a Begonia homonyma mother plant. Young, extended leaves were collected. The plant comes from the Botanical Garden of the University of KwaZulu, South Africa[1].

Evaluate the applied disinfections applied to obtain axenic explants.

There are different disinfectants that have a 100% effect. One is sodium hypochlorite with 70% ethanol plus benlate. Another is Aqueous HgCl (mercuric chloride) 0.2%. At an exposure time of 15min controlled (100%) fungal contamination and provided axenic leaf explants for the in vitro regeneration of Begonia homonyma. If the concentration of HgCl is between 0.1-0.2% and the exposure time only 10 minutes, the controlled fungal contamination is 70%[1].

Which plant growth regulators (PGR) combination was most effective to generate

highest number of shoots?

With 85 shots, the combination of BA (6-benzyladenine [2]) and NAA (-naphthalenic acid [2]) is the most effective method [1].

Which in vitro growth conditions increased root formation?

If you go by the number of roots per shoot the best combination is IBA with NAA with 31.4. Closely followed with 27 roots per shoot is only IBA (indole-3-butyric acid [3]). But if you go by the length of the roots the best combination is IBA with PG (phloroglucinol [3]). The root length for this combination is 82mm. The second highest root length with 60mm was achieved by the combination IBA with NAA [1].

Fig. 1. In vitro plant regeneration via organogenesis from leaf and shoot explants of B. homonyma [1]

Table 1, In vitro protocol Begonia homonyma [1]

Stag of culture	Timeline in weeks	Applied media	Remarks
a	1-12	MS medium supplemented with 15 μM BA and 5 μM NAA.	Induction of shoots   from leaf explants
b	12-18	MS medium supplemented with 15 μM TDZ and 5 μM NAA	Shoot multiplication
c	8	MS medium supplemented with 15 μM TDZ and 5 μM NAA.	Induction of shoots   from callus
d	12	Necrosis of shoots in 15 μM BA and 5 μM NAA.	Necrosis of shoots
e	12	Medium supplemented with 15 μM mTR and 5 μM NAA	Reduced shoot necrosis
f	18	MS medium supplemented with 5 μM GA3 and 0.5 μM BA.	Prolific shoot growth
g	18-30	supplemented with 2 μM GA3 and 0.5 μM BA	Elongation of  shoots
h	30-36	supplemented with 2 μM GA3 and 0.5 μM BA	Rooting of shoots
i	36 and longer	supplemented with 2 μM GA3 and 0.5 μM BA	Acclimation
j	36-44	soil	Acclimation in the greenhouse
k	44-50	soil	Acclimation in the greenhouse

References :

[1] A. Kumari, P. Baskaran, J. Van Staden (2017, January 13). In vitro regeneration of Begonia homonyma - A threatened plant. South African Journal of Botany, pp. 174-177.

[2] Karakas, Fatma Pehlivan (2020 January). Efficient plant regeneration and callus induction from nodal and hypocotyl explants of goji berry (Lycium barbarum L.) and comparison of phenolic profiles in calli formed under different combinations of plant growth regulators. Plant Physilogy and Biochemestry, pp. 384-391

[3] Parveen Shahina, Shahzad Anwar (2014 March). Encapsulation of nodal segments of Cassia angustifolia Vahl. for short-term storage and germplasm exchange, ACTA PHYSIOLOGIAE PLANTARUM, pp. 635-640