SPECIFIC INTERACTION OF MUCOID STRAINS OF PSEUDOMONAS SPP WITH OREGANO (ORIGANUM VULGARE) CLONES AND THE RELATIONSHIP TO PREVENTION OF HYPERHYDRICITY IN TISSUE-CULTURE

Control of hyperhydricity or vitrification in tissue culture has inclu ded modifications of media nutrients and environmental conditions. Rec ently, inoculation of oregano (Origanum vulgare) shoot explants with a Pseudomonas spp. was reported to prevent hyperhydricity (Shetty et al ., 1995). In this report, several different strains of Pseudomonas spp . were isolated and their role in preventing hyperhydricity was invest igated in two oregano clonal lines 0-1 and 0-4. Characteristics of the bacteria include two mucoid producing strains A and F a non-mucoid st rain (NMA) isolated as a spontaneous variant from A, and a nonmucoid s train (NMF) obtained from F through chemical mutagenesis. Hyperhydrici ty was identified based on shoot morphology and related physiological characteristics such as chlorophyll, water, solids, and total phenolic content. prevention of hyperhydricity was observed in shoots of both clonal lines inoculated with mucoid strains A and F and such shoots ha d highest content of total chlorophyll, phenolics, and solids. Shoot e xplants inoculated with non-mucoid strain NMA had partial prevention o f hyperhydricity and intermediate levels of chlorophyll, phenolics, an d solids between mucoid strain inoculation and the uninoculated contro l. Shoots inoculated with the non-mucoid strain NMF Showed hyperhydric ity and had very similar levels of chlorophyll, solids, and phenolics as uninoculated control. This research provides new clues about Pseudo monas spp. interactions with oregano shoot explants and clearly showed that prevention of hyperhydricity in tissue culture was linked to muc oid strains.