PSEUDOMONAS SPP-MEDIATED REGULATION OF TOTAL PHENOLIC AND ROSMARINIC ACID LEVELS IN SHOOT-BASED CLONAL LINES OF THYME (THYMUS-VULGARIS L)

Plant phenolics are secondary plant products, sometimes synthesized as chemical defenses to microorganisms, and also serve as potential sour ces of food preservatives. In this study, we have investigated the ext ent of stimulation of total phenolics and rosmarinic acid (RA) levels in three in vitro shoot culture-based thyme clonal lines in response t o a novel Pseudomonas spp. previously isolated from oregano tissue cul tures. Clonal lines chosen for this study were the high phenolic line T-12 and the medium- and low-phenolic lines T-16G and M-3. Results ind icate that different strains of Pseudomonas stimulated total phenolic levels and RA accumulation to varying degrees. Mucoid strain M4 elicit ed the highest levels of RA in clonal line T-12 an day 25. A moderate degree of RA stimulation in response to M4 was observed in clonal line M-3. Mucoid strain F elicited the highest total phenolic levels in T- 12 on day 25. Nonmucoid strain NMA elicited stimulation of total pheno lic compounds and R4 to some degree only in clonal line T-16G. A 30 da y time course analysis in line T-12 indicated that strains F and NMA e licited the highest phenolic levels. RA synthesis appeared to be stimu lated in response to M4 at later stages of growth and reduced stimulat ion was apparent in response to F and NMA. The mechanical rigidity of T-12 shoots appeared to be highest in response to mucoid strain M4, in dicating the possibility of increased lignin formation. This Pseudomon as-thyme clonal system provides a foundation to investigate the microb ially-elicited stimulation of biosynthetic pathways leading to novel a ntimicrobial and antioxidants.