Plant & Animal Genome VI Conference

W47

PHYSIOLOGICAL AND MOLECULAR RESPONSE OF MARITIME PINE TO PROGRESSIVE WATER DEFICIT

1. INRA - Station De Recherches Forestieres - BP45, F-33610 Cestas FRANCE
2. INRA - UnitÉ D'ecophysiologie Forestiere, F-54280 Champenoux FRANCE

Maritime pine (Pinus pinaster Ait.) is the first conifer species used for reforestation in France. This species is often submitted to drought in summer, limiting its growth capacity. With the aim of developping tolerant genotypes in the breeding programme, we are studying the physiological, genetic and molecular response of young maritime pine seedling to this abiotic stress. Ecophysiological parameters were measured before and during a water deprivation of 6 weeks in a segregate F₂ family (200 two-year old seedlings). These parameters are related with response of plants to drougth: stomatal conductance, predawn water potential, relative water content, water consumption, photosynthesis, osmotical potential, carbon isotope discrimination and growth rate. These traits allowed to estimate osmotic regulation, stomatal control and water use efficiency. A genetic map of the F₁ parent was constructed with PCR-based markers and 2D PAGE proteins. It allowed the detection of QTLs for these traits. Detection and comparative location of (i) QTLs for the same trait measured during the stress (on a weekly basis or before and after the stress), and (ii) of QTLs for different physiological traits, are presented and discussed. QTL accounting for the quantitative variation of drought inducible proteins were also located in the map. Their co-localisation with physiological QTL was studied in order to understand the biological meaning of QTLs. With this approach of identification and characterisation of genomic regions involved in response to water stress, genetic markers could be developed to help selection of maritime pine genotypes for a better water use efficiency.