AN INTEGRATIVE STUDY OF DROUGHT STRESS RESPONSE IN MARITIME PINE

¹ Unite de Recherches Forestieres, INRA Centre de Bordeaux, BP45, 33610 Cestas, France

² Unite d’Ecophysiologie Forestiere, INRA Centre de Nancy, 54280 Champenoux, France

Genetic improvement of forest trees is a very long process compared to that of annual crops. From the selection to the harvesting of improved varieties, via seed production in seed orchards, it may take more than half a century for fast growing conifers. At this scale of time, climatologists have predicted a global change with an increase of temperature. Therefore, the genotypes used in tree breeding programs should be selected for their adaptation to future climatic conditions if major losses are to be avoided. Drought adaptation features have practically not been considered in tree breeding programs so far, namely due to the complex nature of drought resistance. An interdisciplinary effort was recently developed to investigate the physiological, genetic and molecular response of maritime pine (Pinus pinaster) faced to drought. Main attention was given to the photosynthetic tissue. High resolution two-dimensional gel electrophoresis first allowed to identify drought-responsive proteins, further characterized from internal peptide sequences and similarity search in public databases. Trait dissection analysis was then performed in a selfed F2 progeny of 200 two-years-old seedlings based on biochemical (protein quantity) and physiological (photosynthesis, hydric behavior, growth) traits. A saturated genetic map was constructed for mapping PQLs (protein quantity loci) controlling the amount of individual proteins, and QTLs (quantitative trait loci) accounting for part of the phenotypic variation of physiological traits. While numerous genomic regions were involved in a complex regulation of drought stress response at the protein level, only 3 distinct chromosomal regions were implicated at the physiological level. Considering the trait-QTLs and the conditions of trait assessment (non stress vs. stress treatment) a putative role was proposed for each of the three regions : (1) stomatal regulation, (2) photosynthetic capacity and (3) water uptake.