Use of Response Surface Methodology (RSM) to Optimize Culture Media for in vitro Callogenesis in Ipomoea obscura (L.) Ker-Gawl, a Little Known Medicinal Plant

Aims: The present study was undertaken to explore the potentiality of in vitro micropropagation (by callus induction) of Ipomoea obscura(L.) Ker-Gawl (Convolvulaceae), a perennial herb. Method: Axenically grown cotyledonary leaves regenerated into profuse calli, in various combinations of naphthaleneacetic acid (NAA), indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and 2,4dichlorophenoxyacetic acid (2,4 D) with benzylaminopurine (BAP). Microroots emerged from these calli when subjected to various combinations of NAA and BAP. Maximum number of root meristems and microroots were formed in 1.25 mg/L NAA with the combination of 0.5 mg/L BAP (1:4 v/v). Leaf, nodal and internodal segments as explants were cultured on MS media containing 2,4 D at 0.5, 1.25, 2.50, 5.0 and 10.0 mg/L, for callus induction. Only leaf tips initiated callogenesis with highest response at 10 mg/l 2,4 D and lowest with 0.5 mg/l 2.4 D. This is the first report of in vitro response of I. obscura.  Results: All the results were analyzed on the context of response surface methodology (RSM) and simultaneously by contour plot. Two variables lay out in X and Y axes and a third variable Z is plotted for contour level as concentric values. An efficient and effective micropopagation protocol was developed from the leaf of Ipomoea obscura (L.) Ker-gawl, an important medicinal plant. Transplantation of regenerated plants under in vivo condition has been done successfully. RSM has been used for modeling, analyzing and optimizing in vitro responses of Ipomoea obscura. The specific target response surface plot and contour plot are focused to determine optimum shoot and root length against optimum hormone concentration, number of shoot and root length   in best concentration of MS medium and finally mean number of root and shoot in optimum NAA concentration. Depending upon variances of dry weight of callus, rooting response and root length, response surface plots (RSM) and contour plots were drawn  where four types of hormone combinations  (IAA- BAP, IBABAP, NAA-BAP, 2,4D-BAP) were used in different combinations.

Author(s) Details
Dr. Tanmoy Sinha
Cytogenetics and Molecular Biology Unit, Department of Botany, The University of Burdwan, Burdwan-713104, West Bengal, India

A. Bandyopadhyay
Cytogenetics and Molecular Biology Unit, Department of Botany, The University of Burdwan, Burdwan-713104, West Bengal, India.

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