SELECTION OF HIGH PHENOLICS-CONTAINING CLONES OF THYME (THYMUS-VULGARIS L) USING PSEUDOMONAS SP

A high phenolics-containing clonal line (T-12) of thyme (Thymus vulgar is L.) was isolated from a heterogeneous seed population by plant tiss ue culture techniques. This clonal line was isolated from among 10 clo nal lines, with each originating from different genetically heterozygo us, single-germinating seedlings. All clonal lines were generated via shoot organogenesis through adventitious bud proliferation from apex e xplants. Optimum shoot organogenesis was induced on Murashige and Skoo g (MS) medium with benzyladenine (1 mg/L) as the growth hormone. Multi ple shoots originating from apex explants of single heterozygous seedl ings were further multiplied on the aforementioned benzyladenine-conta ining MS medium to subsequently generate a larger number of clonally i dentical plants. Shoots from each individual clonal line were inoculat ed with a novel Pseudomonas sp. Following growth on hormone-free MS me dium for 25 days, total phenolics were determined spectrophotometrical ly. Using this approach, high phenolics-stimulated clonal line T-12 an d moderate phenolics-stimulated clonal time T-16G were isolated. These clonal lines attained the higher level of phenolics following Pseudom onas inoculation and also had uninhibited shoot growth compared with t he corresponding uninoculated control. Several low phenolics clonal li nes, which had inhibited shoot growth in response to Pseudomonas sp., were also isolated. Thymol levels of uninoculated shoots of all clonal lines after 60 days of growth were also measured by gas chromatograph y-mass spectroscopy. The high-to-medium phenolics-containing clonal li nes (T-12 and T-16G) had basal thymol levels in the range of 150 mu g/ g fresh weight (FW). The thymol levels of low phenolics-containing clo nal lines were in the range 10-70 mu g/g FW. This Pseudomonas sp. medi ated selection provides a potentially novel biotechnology based strate gy to isolate high phenolics and thymol-containing clonal lines of thy me from a genetically heterogeneous population.