Enhancement of in vitro propagation efficiency and induction of polyploidy in orchids
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Date
2009
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College of Agriculture, Vellayani
Abstract
Studies were conducted at the Department of Pomology and Floriculture and theDepartment of Plant Biotechnology, College of Agriculture, Vellayani during 2005 - 2008 to enhance the in vitro propagation efficiency and induction of polyploidy in orchids. Commercially important Dendrobium cultivars such as Rungnappa Red, Miss Snow White and Earsakul were selected for the present study. The effects of explant, plant growth regulators, basal culture medium and media supplements during various stages of in vitro propagation were studied. The effect of colchicine in inducing polyploidy under in vitro condition was also studied. Stem nodal explants from kiekies were identified as the best explant for the initial culture establishment of the selected Dendrobium cultivars. Varietal difference in response to plant growth regulators and media supplements was significant among the three cultivars. Half MS medium was found the best basal medium with respect to earliness in bud initiation as well as maximum number of shoots produced. Half MS medium supplemented with kinetin 2.0 mg l-1 + NAA 0.1 mg l-1 gave early bud initiation in cv. Rungnappa Red where as the combination of kinetin 1.0 mg l-1 + NAA 0.1 mg l-1 gave early bud initiation in cv. Miss Snow White. In cv. Earsakul, BA at 4.0 mg l-1 gave early bud initiation. In multiple shoot production stage, in cv. Rungnappa Red, BA 1.0 mg l-1 + NAA 0.1 - 0.5 mg l-1 gave maximum number of shoots. In cv. Miss Snow White maximum number of shoots were observed in BA 0.5 mg l-1 + NAA 0.5 mg l-1 and in cv. Earsakul maximum number of shoots were observed in kinetin 2.0 mg l-1 + NAA 0.1 mg l-1. CW at 200 ml l-1 was found superior with respect to early bud initiation and maximum shoot production in all the three varieties. CH at 1000 mg l-1 gave maximum shoot production in cv. Earsakul. Sucrose at 60.0 g l-1 recorded maximum number of shoots in cv. Rungnappa Red while sucrose at 30.0 g l-1 recorded maximum number of shoots in cv. Miss Snow White. Activated charcoal at 0.5 g l-1 was found beneficial in all the three varieties. The effective concentration of polyamine, spermine for maximum shoot production was at 1.0 mM, 0.5 mM and 1.0 mM in cvs. Rungnappa Red, Miss Snow White and Earsakul respectively. The effective concentration of polyamine, spermidine for maximum shoot production was at 1.0 mM in cvs. Rungnappa Red and Miss Snow White. The optimum concentration of steroid plant growth regulator 28- HBL, that gave maximum shoot numbers in cvs. Rungnappa Red, Miss Snow White and Earsakul were 0.5 mg l-1, 2.0 mg l-1 and 4.0 mg l-1 respectively. Early root initiation in cv. Rungnappa Red as well as in cv. Miss Snow White was observed at 0.5 mg l-1 IBA, and in cv. Earsakul, at 0.5 mg l-1 NAA. The planting out media comprising charcoal and brick pieces in equal proportion gave maximum survival rate in all the three varieties. Shoots regenerated from 0.1 % colchicine treated stem nodes of Miss. Snow White for 5 days were observed to have unusual morphology characterized by slow growing shoots with reduced internodes and thicker and greener leaves.
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