Influence of drought stress on growth, protein expression and osmolyte accumulation in sunflower Helianthus annuus L. c.v. Peredovik

Drought stress causes considerable yield losses in agriculture and receives high attention in current sunflower breeding programs. For this study, an in vitro system based on MS media (Murashige and Skoog, 1962) supplemented with polyethylene glycol 6000 (Korell, 1997) was established to examine sunflower (Helianthus annuus L.) seedlings under artificial drought stress conditions. The objective is to identify parameters applicable as markers for drought stress, which would allow breeders to screen their material efficiently for drought tolerance. For this purpose, different morphological and physiological parameters were analysed by comparing control plants with plants grown under drought stress (-0,6 MPa). The evaluation of growth reveals a significant growth deficit of drought stressed plants compared to control plants concerning hypocotyl length, development of cotyledons and primary leaves, whereas for root fresh weight in relation to shoot fresh weight no significant difference could be detected. Qualitative and quantitative changes in osmolyte accumulation were examined by HPLC and gas chromatography. Osmolyte analyses revealed an accumulation of glucose (25-30fold), inositol (2030fold), proline (10-20fold), fructose (3-6fold) and sucrose (4-5fold) in extracts from leaves of droughtstressed plants. Changes in protein expression of drought-stressed versus control plants were detected in colloidal Coomassie-stained 2D-PAGE gels. In future studies, differentially expressed proteins will be identified by peptide mass fingerprinting and used to develop molecular markers for breeding programs.