Plant & Animal Genome IX Conference Plant & Animal Genome IX Conference
Workshop: Abiotic Stress
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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 components of maritime pine (Pinus pinaster Ait.) response faced to drought. A saturated genetic map was constructed from the segregation of 650 AFLP markers in a three-generation outbreed pedigree. Carbon isotope discrimination was measured on 200 14-year old trees. Four QTLs accounting for 40% of the total phenotypic variation were detected. Candidate genes are now being mapped to search for putative co-localisations with QTLs. These candidate genes were derived from two approaches. On the one hand, a specific group of mRNAs involved in drought stress response was detected using the cDNA-AFLP technique. Roots and needles were sampled from seven week old seedlings raised in hydroponic solution (-0.45 MPa in the stressed medium). A total of 10,000 fragments were screened, from which 1% displayed a clear presence:absence variation. They were cloned and sequenced and verified by Northern or RT-PCR. On the other hand, random sequencing of several hundreds of ESTs in each of the non stressed and stressed root and needles cDNA libraries, provided an estimate of the abundance of the mRNAs in the four libraries. Such ôelectronic Northernsö also allowed to define candidate genes. The SSCP technique is used to map these candidate genes.