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Korana Surdonja, Dipl.-Biol. [email protected] Independent Research group: Abiotic Stress Genomics (until 2016) Supervisor: Dr. Markus Kuhlmann Ph.D. Student since October 2012 Influence of post-anthesis drought stress on barley germination and seedling growth Germination is a complex process where the imbibed mature seed must quickly shift from a maturation state to a germination driven program of development. From the economical point of view this process is of importance because it is part of the first step in the malting process of barley and defines the quality of the malt. During the germination process the plant embryo uses the resources from the endsperm and prepares for seedling growth. The antagonism between the phytohormones gibberelin (GA) and abscisic acid (ABA) is an important factor controlling the transition from embryogenesis to germination in the seed. The ability of the seed to germinate depends on its physiological state. One major factor contributing to this state is determined by stored mRNAs that are translated upon imbibition and are germination essential. The stored transcripts are accumulated both in embryo and endosperm during seed development, most of them are ABA responsive, and their accumulation is affected under challenging environmental conditions, such as drought. In my work, transgenic lines with overexpressed AtNCED6 by embryo and endosperm specific promoters and lines with RNAi suppressed 8’-OH-ABA in embryo are used to investigate their different germination behavior and seedling establishment. The results show that post-anthesis drought stressed seeds have an enhanced germination rate during early stages of germination which correlates with lower ABA levels found in the seedlings. The observed faster germination caused by drought stress brings negative impact on several malting quality parameters. Microarray approach is used to elucidate the role of germination essential transcripts and how is their regulation and accumulation changing under influence of different ABA levels produced in different seed tissues and their role during malting process.