Genetic and metabolic control of grain shape and weight in wheat

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Grain shape and weight in wheat are important yield-related parameters. Knowledge about underlying determinants and mechanisms in wheat is therefore of high economic relevance. We here make use of two unique models displaying increased grain weight by potentially different mechanisms. An introgression, within the genetic background of the high-yield winter wheat variety Prinz, represents a genomic fragment of the synthetic wheat M6, which is related to a quantitative trait locus for grain size, especially grain length. A transgenic line, derived from the winter wheat variety Certo, overexpressing a sucrose transporter gene from barley confers increased grain weight, predominantly related to higher grain width. We plan to analyse characteristics associated with specification of the traits grain size and shape in these models. Histological analyses will be used to identify those grain tissues showing differences in cell number and/or cell expansion. Comprehensive phenotyping of grain development will be performed including tissue-specific transcript, metabolite and hormone profiling in maternal and filial grain organs. Main objective is to understand signalling pathways responsible for cell division and expansion modulations during grain development in response to metabolic signals. Gene networks involved in the regulation of ovary and pericarp growth will be inferred from transcriptome data linked to parallel developmental and physiological studies. The expected outcome will lead to deeper understanding of the physiological, molecular and metabolic network underlying the specification of grain size and weight. Such knowledge in the future will allow breeders to develop strategies to increase yield potential.