Physiological and genetic control of tuber formation

Tuber formation is a plastic and complex, but well-orchestrated sequence of morphological, physiological and biochemical events. The physiological con trol mechanisms of this sequence of events may involve many hormones, but c ertainly gibberellic acids play a dominant role: they affect most steps and are influenced by inducing or non-inducing conditions in a manner consiste nt with effects of these conditions on tuber induction. The genetic control is also complex. Numerous cDNA fragments have been isolated which are spec ifically expressed during tuberization. They can be used in anti-sense orie ntation in transgenic plants to test their possible role in tuberization. I n addition these cDNA fragments are used as genetic marker loci in QTL mapp ing studies and serve as candidate genes to explain phenotypic variation. P rofiles of the importance of QTLs over time may be combined with expression profiles of candidate genes. Such novel approaches offer unique opportunit ies for synergism between physiology, molecular biology and genetics.