Tissue culture based screening for selection of high biomass and phenolic producing clonal lines of lavender using Pseudomonas and azetidine-2-carboxylate

Lavender is a good source of essential oils and phenolic metabolites for food, medicine, and cosmetic applications. Due to cross-pollination, lavender has substantial plant to plant variation and therefore a high degree of genetic inconsistency in the level of phytochemicals produced for diverse applications. Tissue culture methods, using benzyladenine-induced shoot organogenesis, were used to isolate clonal lines originating from individual heterozygous seeds among a heterogeneous seed population to exploit the genetic heterogeneity. Subsequently, in a two-step method, clonal shoots of each clonal line were evaluated for the ability to tolerate Pseudomonas inoculation and various levels (0-200 micromolar) of proline analogue, azetidine-2-carboxylate. On the basis of tolerance to Pseudomonas and proline analogue treatments, multiple shoot forming ability, biomass, rosmarinic acid, total phenolics, and total chlorophyll, 20 separate clonal lines were screened and isolated for further vegetative propagation and evaluation. From the clonal lines isolated, lines LH-14, LH-15, LH-17, and LH-11 showed the best potential for overexpression of phenolic metabolites in response to Pseudomonas and proline analogue.