REDUCTION OF HYPERHYDRICITY IN TISSUE-CULTURES OF OREGANO (ORIGANUM VULGARE) BY EXTRACELLULAR POLYSACCHARIDE ISOLATED FROM PSEUDOMONAS SPP

Hyperhydricity or vitrification is a physiological malformation affect ing tissue culture-based propagation of several plant species. A Pseud omonas spp-mediated approach was recently developed to control hyperhy dricity in oregano. This bacterium-induced prevention of hyperhydricit y helped the establishment of clonal plants in the greenhouse without extensive acclimatization. The prevention of hyperhydricity was specif ically linked to mucoid Pseudomonas spp and was characterized by high chlorophyll and reduced water content in oregano shoots. The focus of research reported in this pager was to purify the extracellular mucoid component from Pseudomonas spp and evaluate the effect on hyperhydric ity in oregano tissue culture. The extracellular mucoid component was purified by ethanol precipitation. This extracellular mucoid component was confirmed to be a polysaccharide using gas chromatography-mass sp ectrometry. The effect of purified polysaccharide to prevent or reduce hyperhydricity was tested in oregano clone 0-1. The polysaccharide pr evented hyperhydricity in oregano with reduced efficiency compared to bacterial inoculation. This was characterized by higher chlorophyll an d reduced water content when compared to uninoculated/untreated oregan o shoots. This confirms that the Pseudomonas spp-mediated hyperhydrici ty reduction in oregano is partially due to its extracellular polysacc haride. This provides a novel approach to develop a media formulation to control hyperhydricity in wide number of plant species where tissue culture is used for clonal propagation.